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EMAproducts(at)aol.com
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 Posted: Sun Feb 06, 2011 2:06 pm Post subject: Pitot Heat |
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Bob, as a 25000+ pilot and a CFI for nearly 50 years the advice you give below is the best info I've seen on any of the websites~~I tell people to turn our AOA system off if they are in icing, why have an instrument give you a bad indication~ I will never heat a vane unless the plane is approved for flight in icing conditions.
Elbie Mendenhall
EM aviation www.riteangle.com
| Quote: | Any time you even THINK you've gathered
some ice, the prudent action is to take
immediate measures to get out . . . 180
turn, change altitude, etc. This (or a similar)
philosophy for icing encounters should have
you breathing easier in a much shorter
period of time . . . and probably before
the pitot tube ices over.
|
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 06, 2011 3:30 pm Post subject: Pitot Heat |
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At 04:55 PM 2/6/2011, you wrote:
| Quote: | Bob, as a 25000+ pilot and a CFI for nearly 50 years the advice you give below is the best info I've seen on any of the websites~~I tell people to turn our AOA system off if they are in icing, why have an instrument give you a bad indication~ I will never heat a vane unless the plane is approved for flight in icing conditions.
Elbie Mendenhall |
I've been chided for being too negative about this topic.
There's a relatively popular notion that, "a little bit
of insurance is better than no insurance." But my teachers
and a simple observation of cause/effect of too many accidents
encourages me not to relax on this stance.
My own experience with ice was a single event and with
an instructor on board who KNEW we were collecting.
I was so busy being a whippy IMC pilot that I didn't
notice. The procedures and approach were textbook.
But the airplane fell out of the flare like a rock.
We'd gathered about 1/2" x 3/4" ridge of ice on
the stagnation point of the leading edge which markedly
changed the flying characteristics of the wing.
Nothing on the windshield. But he calculated later
that we'd picked up perhaps 10-20 pounds of ice on
all leading edges. IAS was working fine, I'd
probably lost some prop efficiency but that wasn't
tested because I didn't need to do a go-around.
My instructor told me he had planned to have me
do a missed approach decided that what he was
witnessing outside was as much additional risk
as he was willing to burden our airplane.
Could that same amount of ice contributed to the
well understood SERIES OF CONDITIONS that lead up
to the majority of accidents? Something I was NOT
then smart enough to NOT to test . . . but my
instructor was.
It was years later that I came to the realization
that I COULD have been a fresh holder of an instrument
rating, I COULD have experienced a go-around
event, which would have put me back into that
cloud layer for 10-15 minutes. While I was grinning
ear-to-ear, keeping all the controllers happy and
the needles centered up, the amount of ice on the
wings for second approach might have been another
matter entirely.
He confided in me that a real missed approach condition
would have called for a climb through the cloud
layer followed by a return to Wichita . . . NOT
a second whack at the attempt. That airplane DID
have a pitot heater and I'm sure it was ON. But
other things were stacking up in a way that told
my instructor that the duration of THIS particular
lesson was going to be cut short.
As a tech writer at Cessna I got to write the POH
and maintenance manual sections for electrically heated
props, de-ice boots, heated windshield patches,
and yes, heated pitot tubes. After all that prose
and poetry about how things were suppose to work
(and would most of the time), the proper advice
to pilots was, "No matter what kind of ice you're
in RIGHT now, you have no way to know what the ice
is like 5 miles ahead. Yes, do turn on all the
insurance you can muster and get the hell out of
there."
I've watched ice gathering on the leading edge
of an engine nacelle on a 727 in climb-out. After
about 30 seconds and perhaps 1/2 inch of build up,
I was just starting to worry about it. It suddenly
disappeared in a flash of vapor. Now THAT is what
I call de-icing! Unless the machine you fly is similarly
equipped . . . well . . . what else needs to be said?
Bob . . . [quote][b]
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pmather
Joined: 17 Sep 2009
Posts: 33
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| Posted: Mon Feb 07, 2011 1:05 am Post subject: Pitot Heat |
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Bob, Bob and Elbie
Thanks for your comments – On this basis I’ll save the wire, switch and weight and just use the pitot unheated. Makes you wonder why so many of the production aircraft have heated pitots and no other ice protection.
Best Regards
Peter
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of EMAproducts(at)aol.com
Sent: 06 February 2011 21:56
To: aeroelectric-list(at)matronics.com
Subject: Pitot Heat
Bob, as a 25000+ pilot and a CFI for nearly 50 years the advice you give below is the best info I've seen on any of the websites~~I tell people to turn our AOA system off if they are in icing, why have an instrument give you a bad indication~ I will never heat a vane unless the plane is approved for flight in icing conditions.
Elbie Mendenhall
EM aviation www.riteangle.com
| Quote: |
Any time you even THINK you've gathered
some ice, the prudent action is to take
immediate measures to get out . . . 180
turn, change altitude, etc. This (or a similar)
philosophy for icing encounters should have
you breathing easier in a much shorter
period of time . . . and probably before
the pitot tube ices over. http://www.matronics.com/Navigator?AeroElectric-List |
01234567
[quote][b]
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JOHN TIPTON
Joined: 17 Sep 2006
Posts: 239
Location: Torquay - England
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| Posted: Mon Feb 07, 2011 1:38 am Post subject: Pitot Heat |
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But then, if one has a 'Gretz' heated pitot tube, which powers the heating automatically, and give a indication as such on the panel - should therefore be a good 'icing' indicator as well
John (RV9a-wings)
[quote] ---
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Feb 07, 2011 5:28 am Post subject: Pitot Heat |
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At 03:58 AM 2/7/2011, you wrote:
| Quote: | Bob, Bob and Elbie
Thanks for your comments – On this basis I’ll save the wire, switch and weight and just use the pitot unheated. Makes you wonder why so many of the production aircraft have heated pitots and no other ice protection. |
Its a legacy FAA thing but I don't think it was
ever well explained to the neophyte flying community.
JUST because you CAN shed some ice on a really useful
instrument system shouldn't be taken as a suggestion
that continued flight into recent discovered icing
conditions is encouraged.
But it was part of an FAA certification for flight
into IMC. Here are relevant paragraphs out of
Part 23:
Sec. 23.1323 Airspeed indicating system.
(a) Each airspeed indicating instrument must be calibrated to indicate
true airspeed (at sea level with a standard atmosphere) with a minimum
practicable instrument calibration error when the corresponding pitot and
static pressures are applied.
(b) Each airspeed system must be calibrated in flight to determine the
system error. The system error, including position error, but excluding the
airspeed indicator instrument calibration error, may not exceed three percent
of the calibrated airspeed or five knots, whichever is greater, throughout
the following speed ranges:
(1) 1.3 VS1 to VMO/MMO or VNE, whichever is appropriate with flaps
retracted.
(2) 1.3 VS1 to VFE with flaps extended.
(c) The design and installation of each airspeed indicating system must
provide positive drainage of moisture from the pitot static plumbing.
(d) If certification for instrument flight rules or flight in icing
conditions is requested, each airspeed system must have a heated pitot tube
or an equivalent means of preventing malfunction due to icing.
(e) In addition, for commuter category airplanes, the airspeed indicating
system must be calibrated to determine the system error during the
accelerate-takeoff ground run. The ground run calibration must be obtained
between 0.8 of the minimum value of V1, and 1.2 times the maximum value of V1
considering the approved ranges of altitude and weight. The ground run
calibration must be determined assuming an engine failure at the minimum
value of V1.
(f) For commuter category airplanes, where duplicate airspeed indicators
are required, their respective pitot tubes must be far enough apart to avoid
damage to both tubes in a collision with a bird.
I don't think the wording of that paragraph has changed
at all in my recollection. But in any case, I've come
to understand that "malfunction due to icing" is a
non-quantified term. There is ice, then there is Ice and
finally, there is ICE. If you check out the kind of ice
a pitot tube is expected to shed in the icing tunnel,
it gives pause to consider how the rest of the airplane
might be holding up.
Bob . . . [quote][b]
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BobsV35B(at)aol.com
Guest
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| Posted: Mon Feb 07, 2011 6:44 am Post subject: Pitot Heat |
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Good Morning Bob,
I tend to disagree with the idea that having a heated pitot tube is not a good thing for airplanes that are not equipped for flight in known ice.
As far as I know, all major airlines fly with pitot heat on at all times, not just in icing conditions. I have flown many airplanes where the pitot iced up as soon as any moisture was encountered. I have also flown airplanes that had what were referred to as icing resistant pitot tubes. Personally, I want a good heated pitot tube on any airplane which is planned to be used for serious transportation. I turn on the heat any time there is any precipitation at all. Snow or rain. It makes no difference, I still want pitot heat.
Ice is where you find it. There are lots of times when you really can't say for certain there will be ice, but you also cannot tell there won't be ice.
Even the FAA has finally recognized that if we do not fly any time there is a cloud in the sky when the temperature is around freezing, we won't do much flying.
I can't give a complete course on ice avoidance in a short message, but there are many conditions where a safe flight can be conducted in areas where ice is a good possibility. We need to learn how to fly on the edge of such conditions and always keep a solid gold way out if icing conditions are encountered. If we are afraid to fly any time there might be ice, we will not get much utility out of our airplanes.
On top of that, I know of no airplane that will handle being flown in continuous heavy icing conditions. The idea of deicing and anti icing equipment is to use that capability to get out of the icing conditions. Having "known ice" capability allows you to step a little closer to icing conditions, but you still have to know when to give it up and get out of Dodge! The ones that make the news are those who stayed in ice when they should have gone elsewhere. Think Roselawn, Indiana, and Buffalo, New York.
I can match hours and experience with any expert or instructor you have quoted about icing encounters, but I won't bore the list with details.
Pitot heat is a GOOD thing to have. Putting ice repellent on a propellor is a GOOD thing to do.
The most important thing about getting near ice is having a plan to get out of it. That is true whether you are flying an RV-4 or a Boeing 747.
As in everything else we aviators do, knowledge is the key to making proper decisions.
Happy Skies,
Old Bob
Do Not Archive
In a message dated 2/7/2011 7:29:14 A.M. Central Standard Time, nuckolls.bob(at)aeroelectric.com writes:
| Quote: | At 03:58 AM 2/7/2011, you wrote:
| Quote: | Bob, Bob and Elbie
Thanks for your comments – On this basis I’ll save the wire, switch and weight and just use the pitot unheated. Makes you wonder why so many of the production aircraft have heated pitots and no other ice protection. |
Its a legacy FAA thing but I don't think it was
ever well explained to the neophyte flying community.
JUST because you CAN shed some ice on a really useful
instrument system shouldn't be taken as a suggestion
that continued flight into recent discovered icing
conditions is encouraged.
But it was part of an FAA certification for flight
into IMC. Here are relevant paragraphs out of
Part 23:
Sec. 23.1323 Airspeed indicating system.
(a) Each airspeed indicating instrument must be calibrated to indicate
true airspeed (at sea level with a standard atmosphere) with a minimum
practicable instrument calibration error when the corresponding pitot and
static pressures are applied.
(b) Each airspeed system must be calibrated in flight to determine the
system error. The system error, including position error, but excluding the
airspeed indicator instrument calibration error, may not exceed three percent
of the calibrated airspeed or five knots, whichever is greater, throughout
the following speed ranges:
(1) 1.3 VS1 to VMO/MMO or VNE, whichever is appropriate with flaps
retracted.
(2) 1.3 VS1 to VFE with flaps extended.
(c) The design and installation of each airspeed indicating system must
provide positive drainage of moisture from the pitot static plumbing.
(d) If certification for instrument flight rules or flight in icing
conditions is requested, each airspeed system must have a heated pitot tube
or an equivalent means of preventing malfunction due to icing.
(e) In addition, for commuter category airplanes, the airspeed indicating
system must be calibrated to determine the system error during the
accelerate-takeoff ground run. The ground run calibration must be obtained
between 0.8 of the minimum value of V1, and 1.2 times the maximum value of V1
considering the approved ranges of altitude and weight. The ground run
calibration must be determined assuming an engine failure at the minimum
value of V1.
(f) For commuter category airplanes, where duplicate airspeed indicators
are required, their respective pitot tubes must be far enough apart to avoid
damage to both tubes in a collision with a bird.
I don't think the wording of that paragraph has changed
at all in my recollection. But in any case, I've come
to understand that "malfunction due to icing" is a
non-quantified term. There is ice, then there is Ice and
finally, there is ICE. If you check out the kind of ice
a pitot tube is expected to shed in the icing tunnel,
it gives pause to consider how the rest of the airplane
might be holding up.
Bob . . . |
[quote][b]
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riggs_la(at)yahoo.com
Guest
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| Posted: Mon Feb 07, 2011 6:54 am Post subject: Pitot Heat |
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My experience has been that you can ice up in a pitot tube without icing up the structure and if you do get into ice inadvertently the last thing you want to happen is loose your airspeed. I am adding the heated pitot tube.
Lynn A. Riggs
BH 656 Kit 22
http://www.vrbo.com/340549
http://www.vrbo.com/297684
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Peter Mather
Sent: Monday, February 07, 2011 2:58 AM
To: aeroelectric-list(at)matronics.com
Subject: RE: Pitot Heat
Bob, Bob and Elbie
Thanks for your comments – On this basis I’ll save the wire, switch and weight and just use the pitot unheated. Makes you wonder why so many of the production aircraft have heated pitots and no other ice protection.
Best Regards
Peter
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of EMAproducts(at)aol.com
Sent: 06 February 2011 21:56
To: aeroelectric-list(at)matronics.com
Subject: Pitot Heat
Bob, as a 25000+ pilot and a CFI for nearly 50 years the advice you give below is the best info I've seen on any of the websites~~I tell people to turn our AOA system off if they are in icing, why have an instrument give you a bad indication~ I will never heat a vane unless the plane is approved for flight in icing conditions.
Elbie Mendenhall
EM aviation www.riteangle.com
| Quote: |
Any time you even THINK you've gathered
some ice, the prudent action is to take
immediate measures to get out . . . 180
turn, change altitude, etc. This (or a similar)
philosophy for icing encounters should have
you breathing easier in a much shorter
period of time . . . and probably before
the pitot tube ices over. http://www.matronics.com/Navigator?AeroElectric-List http://forums.matronics.com http://www.matronics.com/contribution |
012345678901234567
[quote][b]
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tomcostanza
Joined: 19 Oct 2008
Posts: 49
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| Posted: Tue Feb 08, 2011 5:25 am Post subject: Re: Pitot Heat |
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Let me play devil's advocate here.
As a student pilot, on a cold winter morning, after a thorough pre-flight, I took off on a practice xcountry with my instructor. The airspeed indicator failed after a few seconds of climbing, and stayed that way until landing. We both assumed that some melted frost made its way into the pitot, and then froze when we got some altitude. I made a very exciting cross wind landing in gusty conditions with no airspeed indicator. A heated pitot, even an underpowered one, would, I believe, have made it much less exciting.
I got a 24V heated pitot for about $25. I'm putting it in my 12V airplane. I put an eyedropper full of water in it and put it in the freezer for a day. Later I heated it with 12V and the ice melted in less than 30 seconds. Granted the freezer didn't duplicate icing conditions, but as Bob said, if you're in icing conditions, you'll need more than a heated pitot. It may be a placebo, but at a cost of $25, it won't be any worse than a non-heated version.
I'm sure a 25000+ hour pilot can fly an airplane with only a compass and an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel safer.
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_________________
Clear Skies,
Tom Costanza
-- in year 17 of a 3 year project |
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andrew.d.zachar(at)gmail.
Guest
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| Posted: Tue Feb 08, 2011 6:01 am Post subject: Pitot Heat |
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Agreed.
In the flight test world, we use heated pitot for not just ice protection, but also to aid in moisture evaporation. Can't let any moisture get into our precious pressure transducers, and a heated tip does the trick.
__
Andrew Zachar
andrew.d.zachar(at)gmail.com
On Feb 8, 2011, at 8:25 AM, "tomcostanza" <Tom(at)CostanzaAndAssociates.com> wrote:
Snip...
| Quote: | it won't be any worse than a non-heated version.
I'm sure a 25000+ hour pilot can fly an airplane with only a compass and an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel safer.
--------
Clear Skies,
Tom Costanza
|
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mdnanwelch7(at)hotmail.co
Guest
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| Posted: Tue Feb 08, 2011 6:04 am Post subject: Pitot Heat |
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> I got a 24V heated pitot for about $25. I'm putting it in my 12V airplane.
> Clear Skies,
Tom,
It sounds as if you've made up your mind, and if peace of mind is what you're
after, you are the one that gets to make that choice.
The only thing I would caution, though, is make absolutely sure you wire it like
it was originally wired. Find out if the probe was intended to be 'always hot', if if it
had some way to regulate it's heating.
The reason I mention this is I read a few days ago how the Dynon heated probe uses a
microprocessor to heat the tip. I'm simply suggesting you should make sure the probe
you have doesn't use the same type of circuitry.
Here's the reference to the Dynon heated probe I was referring to;
Heating: Principles of Operation
This much-anticipated heated version of Dynon’s AOA/Pitot Probe utilizes a heating mechanism unlike any other heated pitot on the market. The probe is heated by a high-quality nichrome heating element whose temperature is accurately measured and regulated by a microprocessor-based controller. This controller—located in an enclosure which can be mounted in a wing or elsewhere—regulates the heat at the tip of the probe to a constant temperature. There are several advantages to this, including: lower power consumption, increased heating element lifespan, and a much cooler pitot on the ground when de-icing is not necessary. This unique technique ensures that the pitot can be rapidly de-iced when required, but does not needlessly waste electricity when not in icing conditions. While the probe does not operate like a normal heated pitot, it will still get fairly hot in normal ambient temperatures. When turned on, it will regulate its internal temperature to about 70°C to 80°C. To ensure that the heater is working, briefly touch the end of the pitot farthest from the snout after 1 minute of operation and verify that it is warm.
Since you are the one who is going to fly your plane, you should be comfortable with your
choices, just make sure they are good choices.
Mike Welch
[quote][b]
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Ed Anderson
Joined: 10 Jan 2006
Posts: 475
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| Posted: Tue Feb 08, 2011 6:39 am Post subject: Pitot Heat |
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I fly with an heated pitot tube in my Rv-6A - and glad I do. Through
exercising poor judgment, I found myself in IMC conditions over Northen
Georgia at 8500 MSL in clouds. I had thought to "punch through" a thin line
of clouds to get to the clear cold high pressure area behind a cold front.
After a couple of minutes on the gauges, better judgment prevailed and I
turned 180 to get back out of IMC conditions. I noticed ice forming on the
leading edge of my canopy and then on the wing in front of the fuel caps. I
belatedly remembered I had pitot heat and turned it on - approx 5-10 seconds
later the airspeed indicator gave a blip from near zero back to reasonable
indicated (I suspect that was a slug of moisture that a few seconds eariler
had been ice forming on the pilot tube).
The gauges and GPS got me head backs in the right direction and
several tense minutes later I broke out of IMC conditions and made a landing
to spend the night. A bit shaken and vowing never to try to "punch though"
again, I was very appreciative of my heated pitot tube. In all my 10 years
of flying with it - that was the first time I had ever turned it on in
flight. So perhaps not essential for an VFR pilot - I personally do not see
any down side (other than money and a bit of weight) to having one.
FWIW
Ed
--------------------------------------------------
From: "tomcostanza" <Tom(at)CostanzaAndAssociates.com>
Sent: Tuesday, February 08, 2011 8:25 AM
To: <aeroelectric-list(at)matronics.com>
Subject: Re: Pitot Heat
| Quote: |
<Tom(at)CostanzaAndAssociates.com>
Let me play devil's advocate here.
As a student pilot, on a cold winter morning, after a thorough pre-flight,
I took off on a practice xcountry with my instructor. The airspeed
indicator failed after a few seconds of climbing, and stayed that way
until landing. We both assumed that some melted frost made its way into
the pitot, and then froze when we got some altitude. I made a very
exciting cross wind landing in gusty conditions with no airspeed
indicator. A heated pitot, even an underpowered one, would, I believe,
have made it much less exciting.
I got a 24V heated pitot for about $25. I'm putting it in my 12V
airplane. I put an eyedropper full of water in it and put it in the
freezer for a day. Later I heated it with 12V and the ice melted in less
than 30 seconds. Granted the freezer didn't duplicate icing conditions,
but as Bob said, if you're in icing conditions, you'll need more than a
heated pitot. It may be a placebo, but at a cost of $25, it won't be any
worse than a non-heated version.
I'm sure a 25000+ hour pilot can fly an airplane with only a compass and
an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel
safer.
--------
Clear Skies,
Tom Costanza
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=330124#330124
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_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Feb 08, 2011 10:16 am Post subject: Pitot Heat |
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| Quote: | I'm sure a 25000+ hour pilot can fly an airplane with only a compass
and an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel safer.
|
But a 50 hour pilot can learn. When I owned 1K1 I occasionally
had an opportunity to ride around the patch with a new renter.
Never encountered a pilot I wouldn't be willing to rent to.
But virtually all were very panel-fixated in the pattern. Our
little uncontrolled airport hosted numerous no-radio airplanes
and we were a popular touch-n-go stop for other no-radio
airplanes. I felt a lot better about the pilot who flew
the airplane confidently with his head out of the cockpit
as opposed to the ones whose comfort was based on keeping all
the needles pointed to some number.
For several pilots, I demonstrated how we could cover
up the basic six and go around the patch with great
confidence that the airplane was well inside normal
operating envelopes. I encouraged folks to stick
the cowl right on the horizon at full throttle and
note the airspeed. Shorter pilots got smaller numbers,
taller pilots got higher numbers. But none discovered
a number that was any cause for alarm and all were
within 5 mph of each other.
Then I would demonstrate that you cannot stall the
airplane without bringing the nose above the horizon
at any power setting.
So with the gages covered up we went around the patch
4 or 5 times and concentrated on that wonderful view
of the Kansas countryside and other airplanes who were
sharing the view with us.
You don't have to cover the gages but you CAN spend
some time in the airplanes you fly most to explore
exactly what significance all those pointers have
with respect to comfortable and confident operation
of the airplane. Every pilot has to do the biennial
check ride in accordance with the predictable and
repeatable demonstration of those skills we were
taught by our instructors. But the really competent
pilot has (for lack of a better term) a certain amount
of "oneness" with the machine. He/she is confident
and competent in the operation of the airplane
well inside the borders of limits envelopes without
reference to the instruments.
There's been some sentiments about the value in
KNOWING the indicated airspeed while doing what ever
it is that good pilots do to deal with a recently
discovered icing condition.
Okay, you're in some stable flight configuration
of climb, cruise or descent and you discover an
icing condition. What kinds of maneuvers would
the good pilot conduct to make the situation better?
Steep turns to do the fast 180? Reduce power?
Increase power? Large changes in pitch? What ever
the decision might be, which of those actions
re-configure the airplane to the edge of the
performance envelope with attendant increase in risk?
The greatest risks for accumulation of ice come
from a combination of increased weight, increased
drag and altered airfoil performance. As I related
in my previous story, ice collecting on the
leading edge had the effect of a marked increase in stall
speed. Okay, once you've got ice on the airplane,
what does the properly functioning IAS indicator
KNOW about departures in 'normal' numbers. Does
the white arc change endpoints in concert with ice
accretion to give the pilot a heads-up on those
departures?
We've read a lot of dark-n-stormy night stories
about pilots who wiggled this, switched that,
explored the other thing in some attempt to add
to their knowledge of what's going wrong with
an electrical system. Virtually all the stories
only served to highlight the pilot's lack of
understanding about how the system worked. In
some cases, fiddling and twiddling made things
worse. At the same time, while the pilot was
playing the role of systems analyst, he was not
being a competent pilot.
The same hard, cold truths of life apply to an airplane
that is found to be collecting ice. This is a
SYSTEM FAILURE that may degrade to a un-recoverable
departure if not addressed with a well considered
plan-B.
The idea that your otherwise friendly IAS indicator
is a dependable tool in carrying out plan-B is problematic.
You already KNOW that the airplane is going to slow down
due to drag. You already KNOW that maintaining altitude
will eventually become problematic due to weight
and drag. You already KNOW that the numbers
represented by the values at the bottom of the white
arc cannot be trusted for the purposes of maneuvering
close to while still avoiding a stall. You're well
advised not to make changes in power settings or to
conduct maneuvers that squander your performance envelope
edge-margins especially when those edges are no longer
predicable.
Like flying in thunderstorms, flying in icing conditions
is an environment where airspeed indications are
unreliable and not terribly significant for avoiding
the unforgiving and possibly terminal stall. Attitude
and power changes that take you to the performance
edges are demonstrably risky. I suggest that the
prudent plan-B for icing does not depend on IAS indications.
Even if the IAS system is working, the data displayed
is purely informational . . . as is your GPS ground
speed. It's no longer a finely calibrated tool for
helping you put some tire-streaks on the numbers.
IAS can only display trends. If the trend is in the
wrong direction, then plan-B has failed you . . . and
there's probably not much else to be done. You might
also be surprised when the airplane falls out of
the sky at 20 kts above the bottom of the white arc.
The point to be considered exactly what value the
displayed IAS data brings to the plan-B party.
Bob . . .
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BobsV35B(at)aol.com
Guest
|
| Posted: Tue Feb 08, 2011 1:42 pm Post subject: Pitot Heat |
|
|
Good Afternoon Bob,
For once I totally disagree with your premise.
The heated pitot tube and a reliable airspeed indicator is a handy tool to have.
If we subscribe to your thought, why bother having an airspeed indicator at all?
When I soloed in the spring of 1946, I was flying a J-3 cub and I never saw the airspeed indicator until the instructor got out of the airplane and told me to take it around the patch three times then bring it over to the gas pit.
When I fly my Stearman today, I rarely look at the airspeed.
However, when I charge out for the West Coast in my Bonanza, I really like having an instrument that will tell me if I am not getting the airspeed indication I expect when flying at certain attitudes and power settings. It is not a "tell all" instrument, but it IS a handy thing to have and a heated pitot tube allows it to be reliable if I pick up a trace of ice while climbing or descending through a thin cloud layer.
Ice is to be respected, but need not be feared if one understands the principle.
Carburetor heat is handy to have, but the engine runs better if you can fly where it is not needed.
The propellor will work better if you think to coat it with a good ice repellent than it will if you get a little more ice than planned while climbing or descending through that thin layer.
The FAA tells us that we are expected to ask for a clearance out of the icing conditions if they are unexpectedly encountered. As long as we have planned a suitable exit strategy, no foul and no careless or reckless citation.
I figure that if something as light weight and simple as a heated pitot tube or ice repellent on the prop gives me a small edge when unexpected icing conditions are encountered, it is a good thing. Avoiding that little piece of ice that may cause my airspeed indicator to become less reliable is well worth the trouble of installing a heated pitot tube and rubbing a bit of ice repellent on the propellor.
I don't have a heated pitot tube on our Piper Pacer and it is flown IFR any time it is practical to do so. The airspeed is lost a lot and one of the things I will do if I ever find time to do it is add a heated pitot tube. I think my skill set will allow me to fly as well as any other pilot without an airspeed indicator, but why do so when it is so easy to have it working?
Happy Skies,
Old Bob
In a message dated 2/8/2011 12:16:55 P.M. Central Standard Time, nuckolls.bob(at)aeroelectric.com writes:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
| Quote: | I'm sure a 25000+ hour pilot can fly an airplane with only a compass
and an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel safer.
|
But a 50 hour pilot can learn. When I owned 1K1 I occasionally
had an opportunity to ride around the patch with a new renter.
Never encountered a pilot I wouldn't be willing to rent to.
But virtually all were very panel-fixated in the pattern. Our
little uncontrolled airport hosted numerous no-radio airplanes
and we were a popular touch-n-go stop for other no-radio
airplanes. I felt a lot better about the pilot who flew
the airplane confidently with his head out of the cockpit
as opposed to the ones whose comfort was based on keeping all
the needles pointed to some number.
For several pilots, I demonstrated how we could cover
up the basic six and go around the patch with great
confidence that the airplane was well inside normal
operating envelopes. I encouraged folks to stick
the cowl right on the horizon at full throttle and
note the airspeed. Shorter pilots got smaller numbers,
taller pilots got higher numbers. But none discovered
a number that was any cause for alarm and all were
within 5 mph of each other.
Then I would demonstrate that you cannot stall the
airplane without bringing the nose above the horizon
at any power setting.
So with the gages covered up we went around the patch
4 or 5 times and concentrated on that wonderful view
of the Kansas countryside and other airplanes who were
sharing the view with us.
You don't have to cover the gages but you CAN spend
some time in the airplanes you fly most to explore
exactly what significance all those pointers have
with respect to comfortable and confident operation
of the airplane. Every pilot has to do the biennial
check ride in accordance with the predictable and
repeatable demonstration of those skills we were
taught by our instructors. But the really competent
pilot has (for lack of a better term) a certain amount
of "oneness" with the machine. He/she is confident
and competent in the operation of the airplane
well inside the borders of limits envelopes without
reference to the instruments.
There's been some sentiments about the value in
KNOWING the indicated airspeed while doing what ever
it is that good pilots do to deal with a recently
discovered icing condition.
Okay, you're in some stable flight configuration
of climb, cruise or descent and you discover an
icing condition. What kinds of maneuvers would
the good pilot conduct to make the situation better?
Steep turns to do the fast 180? Reduce power?
Increase power? Large changes in pitch? What ever
the decision might be, which of those actions
re-configure the airplane to the edge of the
performance envelope with attendant increase in risk?
The greatest risks for accumulation of ice come
from a combination of increased weight, increased
drag and altered airfoil performance. As I related
in my previous story, ice collecting on the
leading edge had the effect of a marked increase in stall
speed. Okay, once you've got ice on the airplane,
what does the properly functioning IAS indicator
KNOW about departures in 'normal' numbers. Does
the white arc change endpoints in concert with ice
accretion to give the pilot a heads-up on those
departures?
We've read a lot of dark-n-stormy night stories
about pilots who wiggled this, switched that,
explored the other thing in some attempt to add
to their knowledge of what's going wrong with
an electrical system. Virtually all the stories
only served to highlight the pilot's lack of
understanding about how the system worked. In
some cases, fiddling and twiddling made things
worse. At the same time, while the pilot was
playing the role of systems analyst, he was not
being a competent pilot.
The same hard, cold truths of life apply to an airplane
that is found to be collecting ice. This is a
SYSTEM FAILURE that may degrade to a un-recoverable
departure if not addressed with a well considered
plan-B.
The idea that your otherwise friendly IAS indicator
is a dependable tool in carrying out plan-B is problematic.
You already KNOW that the airplane is going to slow down
due to drag. You already KNOW that maintaining altitude
will eventually become problematic due to weight
and drag. You already KNOW that the numbers
represented by the values at the bottom of the white
arc cannot be trusted for the purposes of maneuvering
close to while still avoiding a stall. You're well
advised not to make changes in power settings or to
conduct maneuvers that squander your performance envelope
edge-margins especially when those edges are no longer
predicable.
Like flying in thunderstorms, flying in icing conditions
is an environment where airspeed indications are
unreliable and not terribly significant for avoiding
the unforgiving and possibly terminal stall. Attitude
and power changes that take you to the performance
edges are demonstrably risky. I suggest that the
prudent plan-B for icing does not depend on IAS indications.
Even if the IAS system is working, the data displayed
is purely informational . . . as is your GPS ground
speed. It's no longer a finely calibrated tool for
helping you put some tire-streaks on the numbers.
IAS can only display trends. If the trend is in the
wrong direction, then plan-B has failed you . . . and
there's probably not much else to be done. You might
also be surprised when the airplane falls out of
the sky at 20 kts above the bottom of the white arc.
The point to be considered exactly what value the
displayed IAS data brings to the plan-B party.
Bob . . .
|
[quote][b]
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nuckolls.bob(at)aeroelect
Guest
|
| Posted: Tue Feb 08, 2011 4:30 pm Post subject: Pitot Heat |
|
|
At 04:33 PM 2/8/2011, you wrote:
| Quote: | Good Afternoon Bob,
For once I totally disagree with your premise.
The heated pitot tube and a reliable airspeed indicator is a handy tool to have. |
"Handy" is not quantified or qualified. My
premise is that there are times when accurate
IAS improves on the pilot's ability to perform
and reduces risks
| Quote: |
If we subscribe to your thought, why bother having an airspeed indicator at all? |
I don't think you understood the thought . . .
| Quote: |
When I soloed in the spring of 1946, I was flying a J-3 cub and I never saw the airspeed indicator until the instructor got out of the airplane and told me to take it around the patch three times then bring it over to the gas pit.
When I fly my Stearman today, I rarely look at the airspeed.
However, when I charge out for the West Coast in my Bonanza, I really like having an instrument that will tell me if I am not getting the airspeed indication I expect when flying at certain attitudes and power settings. It is not a "tell all" instrument, but it IS a handy thing to have and a heated pitot tube allows it to be reliable if I pick up a trace of ice while climbing or descending through a thin cloud layer. |
Okay, let's assume "handy" means "information
useful for monitoring/trimming performance"
| Quote: | | Ice is to be respected, but need not be feared if one understands the principle. |
agreed
| Quote: |
Carburetor heat is handy to have, but the engine runs better if you can fly where it is not needed. |
not relevant to my premise
| Quote: |
The propellor will work better if you think to coat it with a good ice repellent than it will if you get a little more ice than planned while climbing or descending through that thin layer.
|
also not relevant to the premise
If I perceive the concerns of our readers correctly,
there are embedded notions that a heated pitot tube
offers increased comfort for the reduction of risk
(often called "safety").
The scenarios you've just described speak to matters
of non-critical information that assist the pilot in
fine-tuning or monitoring navigation or performance
of the airplane.
Same ideas apply to moving map displays, autopilots
with every feature including the kitchen sink, etc.
etc. But as pilots, we should be quite capable of
getting from point A to point B with none of those
accessories.
Help me illustrate premise:
Suppose you're cruising along in your C-172 with a
heated pitot tube and you become aware of accumulating
ice. Paint a scenario for the next few minutes of flight
were the IAS display would (a) figure into your action plan
or (b) cause you to change flight configuration with respect
to attitude, altitude or power? Flip side of the same
coin is to consider how your behaviors would be modified
if the pitot tube were not heated and you found the needle
stuck at the last good reading? How would you become aware
that the IAS was stuck due to freezing? Once you confirm
that particular failure, how would that information figure
into subsequent actions. This is an exercise in failure mode
effects analysis for the purpose of crafting a minimum risk
plan-B.
As you've pointed out, there are displays on the panel that
provide data that beg timely response; other
displays that are nice to know. Sometimes, both kinds of
information comes from the same instrument. The information
we seek now are when and how would IAS readings drive decisions
that would reduce risk for extracting one's rear end from
an icing situation?
Bob . . . [quote][b]
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nuckolls.bob(at)aeroelect
Guest
|
| Posted: Wed Feb 09, 2011 6:16 pm Post subject: Pitot heat |
|
|
At 06:47 PM 2/9/2011, you wrote:
| Quote: |
I'm sure a 25000+ hour pilot can fly an airplane with only a compass and
> an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel
> safer.
I personally take offence at the off-handed remark. <snip> |
Gently my friend, he was only voicing his
personal trepidation no doubt borne out
of a sense of his own ignorance and low
position on the totumpole of experience.
We were all there once. It's a fair bet
that a 25K hour pilot has at least learned
a few things that added to his/her longevity
and made them eligible for admission to the
priesthood.
| Quote: | | . There have been very few regulations made without blood being shed. |
Indeed, that has ALWAYS been the overtly
admitted goal for those-who-know-more-about-
airplanes-than-we-do. And indeed, many
regulations have obvious, demonstrable benefits
. . . but not all . . . especially when
misunderstood and misapplied. Witness the recent
discussion on the need for adding battery boxes
to SVLA batteries.
I will suggest that there's an ever-increasing
flood of regulations that have no relationship
to anyone's loss of blood and a lot to do with
empire building.
I hypothesized a C-172 taking on ice . . .
the pitot system IS heated and offers a degree of
confidence. My invitation to the List was to
consider how, and under what conditions the IAS
indicator was useful for reducing risk. E.g.
in a deteriorating situation, at what IAS number
do you "get really concerned" and once that point
is reached, what's the next step?
I have further hypothesized that having a believable
IAS reading under this scenario is of little or
no value for reducing risks. By the time the airplane
is sufficiently crippled as to produce an IAS
value of concern, I've suggested that there is no
action to take where precise IAS is useful feedback
for good pilotage.
Rather than taking whacks at our newby friend
for voicing valid feelings, how can we team
up with must be hundreds of thousands of hours
of total experience on this List to reinforce,
refute, or refine the basis for his feelings?
Bob . . . [quote][b]
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mapratherid(at)gmail.com
Guest
|
| Posted: Thu Feb 10, 2011 4:49 am Post subject: Pitot heat |
|
|
Hey Mr. Nuckolls..
So, my question is, what do you do after the icing encounter? Say you've been lucky (or prudent), and extricated yourself and the contents of the airplane from the icing conditions.. Now do you just have to go somewhere else and land and wait for the bird to dry/thaw? What if there's an alternate route available that avoids the icy conditions, but is less desirable for other reasons (around the mountain range vs over the pass)? Maybe you want to gauge how much cruise speed the airplane has lost because of the ice. Certainly GPS groundspeed can give you an idea about the remaining performance, but being able to cross check with IAS is nice. While I agree that a heated pitot might give some people false confidence, it seems to me there's some utility in one.
Matt-
On Feb 9, 2011, at 6:10 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] At 06:47 PM 2/9/2011, you wrote:
| Quote: |
I'm sure a 25000+ hour pilot can fly an airplane with only a compass and
> an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel
> safer.
I personally take offence at the off-handed remark. <snip> |
Gently my friend, he was only voicing his
personal trepidation no doubt borne out
of a sense of his own ignorance and low
position on the totumpole of experience.
We were all there once. It's a fair bet
that a 25K hour pilot has at least learned
a few things that added to his/her longevity
and made them eligible for admission to the
priesthood.
| Quote: | | . There have been very few regulations made without blood being shed. |
Indeed, that has ALWAYS been the overtly
admitted goal for those-who-know-more-about-
airplanes-than-we-do. And indeed, many
regulations have obvious, demonstrable benefits
. . . but not all . . . especially when
misunderstood and misapplied. Witness the recent
discussion on the need for adding battery boxes
to SVLA batteries.
I will suggest that there's an ever-increasing
flood of regulations that have no relationship
to anyone's loss of blood and a lot to do with
empire building.
I hypothesized a C-172 taking on ice . . .
the pitot system IS heated and offers a degree of
confidence. My invitation to the List was to
consider how, and under what conditions the IAS
indicator was useful for reducing risk. E.g.
in a deteriorating situation, at what IAS number
do you "get really concerned" and once that point
is reached, what's the next step?
I have further hypothesized that having a believable
IAS reading under this scenario is of little or
no value for reducing risks. By the time the airplane
is sufficiently crippled as to produce an IAS
value of concern, I've suggested that there is no
action to take where precise IAS is useful feedback
for good pilotage.
Rather than taking whacks at our newby friend
for voicing valid feelings, how can we team
up with must be hundreds of thousands of hours
of total experience on this List to reinforce,
refute, or refine the basis for his feelings?
Bob . . .
[b]
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tomcostanza
Joined: 19 Oct 2008
Posts: 49
|
| Posted: Thu Feb 10, 2011 5:12 am Post subject: Re: Pitot Heat |
|
|
| Quote: | I'm sure a 25000+ hour pilot can fly an airplane with only a compass and
> an oil pressure gauge. But as a 200 hour wimpy VFR pilot, I'll feel
> safer.
I personally take offence at the off-handed remark. I once was a new
pilot, have trained hundreds a CFI since '62 and I made no comments other than
to agree with Bob, whom all respect or they wouldn't be on the list.
Perhaps after you have made as many mistakes as I did early in my career you
will realize there are very few old, bold pilots and enjoy your flying as
much as I have the last 49 years. There have been very few regulations made
without blood being shed.
Elbie Mendenhall |
I apologize for my compliment. I would have sent a private email, but since the offense was made before the group, I thought the apology should be too.
With respect,
-Tom
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_________________
Clear Skies,
Tom Costanza
-- in year 17 of a 3 year project |
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Neal.George(at)hurlburt.a
Guest
|
| Posted: Thu Feb 10, 2011 6:45 am Post subject: Pitot heat |
|
|
I think y'all are still missing the point.
With the airplane picking up ice, the stall speed changes with the accretion. The type of ice, shape, amount and location all affect the performance of the aircraft. You won't find performance parameters for your iced-up airframe in the POH.
A few things you don't know - CAN'T know - with ice on the airframe:
1) How much ice is on the airplane? Quantify it.
2) What does the ice weigh? Again, hard numbers.
3) How fast is the ice accumulating?
4) When will the weight of ice push the airplane over gross weight?
5) When will the airplane stop flying because of the ice it has accumulated?
6) With x amount of ice on the airframe, what's the stall speed?
Let's imagine Capt Super Stud bores thru a low cloud with OAT in the teens and finds some ice. Doesn't really matter what kind of ice - it's sticking to the airframe and accumulating. Let's give him the benefit of the doubt and a little luck and say there's a runway close and straight ahead and he's smart enough to choose to land. It's VFR at pattern altitude, so he joins the downwind for a standard pattern - got it made, no sweat. 80-kts on downwind, 70-kts on base, and he falls out of the base-to final turn because the ice has changed his stall speed.
The point is, an accurate indicated airspeed is of little use where it matters - near the stall end of the envelope - if you don't know what the stall speed is in the airplane's current iced-up condition.
neal
--
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nuckolls.bob(at)aeroelect
Guest
|
| Posted: Thu Feb 10, 2011 7:19 am Post subject: Pitot heat |
|
|
At 07:42 AM 2/10/2011, you wrote:
Hey Mr. Nuckolls..
So, my question is, what do you do after the icing encounter? Say
you've been lucky (or prudent), and extricated yourself and the
contents of the airplane from the icing conditions.. Now do you just
have to go somewhere else and land and wait for the bird to
dry/thaw? What if there's an alternate route available that avoids
the icy conditions, but is less desirable for other reasons (around
the mountain range vs over the pass)? Maybe you want to gauge how
much cruise speed the airplane has lost because of the ice. Certainly
GPS groundspeed can give you an idea about the remaining performance,
but being able to cross check with IAS is nice. While I agree that
a heated pitot might give some people false confidence, it seems to
me there's some utility in one.
Yes, there's 'utility' or as Bob suggested,
'handiness'. My premise was that IAS is not high
on the list of data items that drive risk reducing
behavior . . . i.e. increase in safety under
icing conditions.
GPS is the system used to calibrate IAS and
ground speed is going to be much more useful
for determining ETA to an alternate airport
than IAS . . . working well or not.
Once you've arrived at a comfortable alternate,
and your airplane is still carrying ice, my
personal experience suggests that IAS, working
or not, is still a shakey foundation for
executing a graceful arrival. My approach would
arrive over the numbers flat and fast . . . fly
it on and concentrate on holding directional
control as opposed to the customary quest for a
'greaser'.
Once the airplane is iced up, the rules by
which we normally conduct comfortable flight
are changed. Further, the new rules are relatively
unknown to the pilot who seldom, if ever,
encounters the situation. Lessons learned from
my one and only encounter were profound.
No doubt there are individuals in our numbers
who have encountered icing conditions numerous
times and have acquired comfort levels consistent
with their experience in their choice of airplanes.
My question to the List goes to the notion of
advising our 200 hour VFR friend that having a
heated pitot offers any quantum improvements in
risk-reduction. The simple-ideas under which ice,
airplanes, instrumentation and pilots interact do not
seem to support the advice. In my own experience,
I was using good IAS data right down to the point
where the airplane suddenly refused to fly. But
I'd be pleased to be corrected if that deduction
can be shown to be in error.
Bob . . .
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tomcostanza
Joined: 19 Oct 2008
Posts: 49
|
| Posted: Thu Feb 10, 2011 7:54 am Post subject: Re: Pitot Heat |
|
|
| Quote: | My question to the List goes to the notion of
advising our 200 hour VFR friend that having a
heated pitot offers any quantum improvements in
risk-reduction. |
Perhaps I wasn't clear in my post. I wasn't in icing conditions. Conditions were CAVU. The iced pitot was caused by moisture, liquid on the ground, ice after takeoff. There was no ice anywhere else. So my only comment was that I'd rather land with an airspeed indicator than without one. My cost was $25 for a used heated pitot, about $10 for a switch, plus a few feet of wire. If the cost/benefit was calculated with a $600+ new heated pitot, I may have decided differently. I'll stipulate that I should be able to land safely without one. But when you look at accident reports, one thing that usually stands out is that there was a chain of events leading to the accident. Break the chain, and you would probably avoid the event. Landing without an airspeed indicator is a distraction I can easily avoid.
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Clear Skies,
Tom Costanza
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