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Cowling update

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GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Sat Aug 30, 2008 11:15 am Post subject: Cowling update

Now, it looks like I need to validate the climb performance from the POH. Â Great. Â The plane has a 65 inch pitch prop. Â This should be fun. 

 

  Why do I need to do a climb test? Â Just incase I increased the drag on the plane with my new cowling. Â 

 Get the MapQuest Toolbar. Directions, Traffic, Gas Prices & More! 

  [quote][b]

_________________
Gary
AuCountry Aviation
Home of Team Grumman

flyv35b(at)minetfiber.com
Guest

Posted: Mon Sep 01, 2008 12:32 pm Post subject: Cowling update

What about the data from the climb cooling test?   Shouldn't that be sufficient?  Wasn't it done at Vy?

  

 Cliff

 [quote]   ---

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Mon Sep 01, 2008 7:42 pm Post subject: Cowling update

Hi Cliff,Â  

 

  Yes, it was done at Vy, but, we didn't time the climb for each increment in the POH. Â It's BS, I know. Â But, what can I do?

 

 

 --

_________________
Gary
AuCountry Aviation
Home of Team Grumman

ski2little(at)AOL.COM
Guest

Posted: Tue Sep 02, 2008 3:10 am Post subject: cowling update

Not surprised FAA requires a climb test - presumably to confirm the plane can still climb at least as well as stock plane - at gross weight.  I'm more surprised this was a surprise.Get the MapQuest Toolbar. Directions, Traffic, Gas Prices & More! 

  [quote][b]

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Tue Sep 02, 2008 11:45 pm Post subject: cowling update

Climb performance is more of a function of excess horsepower and weight than drag. Â At Vy, induced drag is more of a player in overall drag than is parasitic drag. Â Induced drag would be more of a function of airfoil design than cowling design.

  

 

 The questions should be: Â  Â Â (1) do any of the planes climb at book values?

  Â Â (2) what prop was used for the book values? Â 61 inch, 62 inch, 63 inch, 64, inch or 65 inch pitch?

      (by-the-way, the POH has climb performanceÂ for various weights, not just gross weight)

  Â Â (3) what were the conditions under which the tests were performed. Â i.e.,Â were the numbers in the POH

  Â Â   A. extrapolated from a continuous climb at Vy to various altitudes?

      B. evaluated for climb rate from a stabilized level flight condition and a maximum airspeedÂ 

          to a specified altitude then re-stabilizing level flight and repeating?

  Â Â 

  Why am I surprised? Â The only issue should be if I increased the drag on the cowling then climb performance would come into question. Â A more indicative test would be fuel flow at various altitudes and airspeeds. Â A test like this would indicate if the cowling affe cted the overall drag. Â 

 

 

 

  

 

  

 --

_________________
Gary
AuCountry Aviation
Home of Team Grumman

flyv35b(at)minetfiber.com
Guest

Posted: Wed Sep 03, 2008 4:47 am Post subject: cowling update

I think where the ball got dropped is that the FAA  should have outlined and specified what tests were required at the beginning of  the program.  Not done it piecemeal and at the last minute said  2oh, by the  way, you need to do a climb test 2!  Although they can do this, it isn't the  way they are supposed to handle these STC programs.  You should have been  notified about this test requirement a long time ago and the test could have  been incorporated with the cooling climb test.

  

 Cliff

 [quote]   ---

aa1bflyboy

Joined: 23 May 2008
Posts: 30

Posted: Wed Sep 03, 2008 5:02 am Post subject: cowling update

Hey Cliff we are talking about the government remember... LOL



We shall not cease from exploration.

And at the end of all our exploring

Will be to arrive were we started

And know the place for the first time - T. S. Eliot



Steve Roberts - AA-1B N641HY (at) ILG





----Original Message Follows----

From: "flyv35b" <flyv35b(at)minetfiber.com>

Reply-To: teamgrumman-list(at)matronics.com

To: <teamgrumman-list(at)matronics.com>

Subject: Re: re:cowling update

Date: Wed, 3 Sep 2008 05:47:20 -0700



I think where the ball got dropped is that the FAA should have outlined and 

specified what tests were required at the beginning of the program.  Not 

done it piecemeal and at the last minute said "oh, by the way, you need to 

do a climb test"!  Although they can do this, it isn't the way they are 

supposed to handle these STC programs.  You should have been notified about 

this test requirement a long time ago and the test could have been 

incorporated with the cooling climb test.



Cliff

   ---

_________________
Steve Roberts

pitts_pilot(at)bellsouth.
Guest

Posted: Wed Sep 03, 2008 5:08 am Post subject: cowling update

Years ago I was TDY in San Louis Obispo and attended an EAA chapter 

meeting.  The speaker used the numbers in a Piper owners manual to show 

how using the numbers in certain situations could ruin your whole day.  

It turns out that he was one of Bedes test pilots on the AA-1.  I think 

that test methods used way back when probably aren't applicable to 

todays environment.  But that observation comes from limited exposure to 

the FAA as I can. 

Linn

teamgrumman(at)aol.com wrote:

 	  Quote: 	
		   Climb performance is more of a function of excess horsepower and 

 weight than drag.  At Vy, induced drag is more of a player in overall 

 drag than is parasitic drag.  Induced drag would be more of a function 

 of airfoil design than cowling design.



 The questions should be:  

   (1) do any of the planes climb at book values?

   (2) what prop was used for the book values?  61 inch, 62 inch, 63 

 inch, 64, inch or 65 inch pitch?

 (by-the-way, the POH has climb performance for various weights, not 

 just gross weight)

   (3) what were the conditions under which the tests were performed. 

  i.e., were the numbers in the POH

    A. extrapolated from a continuous climb at Vy to various altitudes?

 B. evaluated for climb rate from a stabilized level flight condition 

 and a maximum airspeed 

 to a specified altitude then re-stabilizing level flight and repeating?

   

 Why am I surprised?  The only issue should be if I increased the drag 

 on the cowling then climb performance would come into question.  A 

 more indicative test would be fuel flow at various altitudes and 

 airspeeds.  A test like this would indicate if the cowling affe cted 

 the overall drag.

flyv35b(at)minetfiber.com
Guest

Posted: Wed Sep 03, 2008 5:50 am Post subject: cowling update

I can tell you one thing: If you believe the takeoff distance (ground roll 

and over a 50 ft obstacle) performance numbers in an AA-1XX POH for higher 

density altitude takeoffs you are in for a rude awakening unless you leave 

LOTS of reserve.



Cliff

---

robsherwin(at)AOL.COM
Guest

Posted: Tue Sep 16, 2008 7:59 pm Post subject: cowling update

The same is true of the AA5 (and AA5A) POH's.  The Tiger POH is much more realistic.  The high, and especially the high and hot, for the Cheetah's take distance get increasingly ridiculous.  Compare the take off distance over 50' at standard temp at 8,000.  For the Cheetah, it's 2,700 but for the Tiger it's about 3,450.  How can that be?  The Cheetah takes longer at sea level to take off and has a significantly lower service ceiling.  There is no way that it is magically that much better than the Tiger just when it's high (and/or hot).  We all know that's when those of us that have 150 bhp wish for 160 (or more).

 

 By the way, Gary, I now own Kevin Loftus 9853U (since '04).  She flies like a champ still (except for that density altitude thing).

 

 Rob

 

 

 --

mkaratsonyi(at)hotmail.co
Guest

Posted: Wed Sep 17, 2008 10:05 am Post subject: cowling update

hello all C

 i have a 1978 grumman aa1-c with the original 0235 L2C i am located in southern ca. my question is i recently flew with a passenger with only using 365lbs of my 489 useful load minus 6-8 gal of gas. i departed van nuys and slowly climbed to 2300' after about maybe 10 min of flight i noticed oil temp was 290 or so ..close to yellow/red on gauge so i leveled out full rich and pull rpm back to 2100rpm it slowly cooled but what i noticed and what my question is ...is that cabin heat was off and vents full open(oh by the way i had canopy open) it was 70 degrees outside nice and cool but vents were blowing out hot air i verified and cycled cabin heat it got hotter shut it off but still warm....does anyone anything about this...thanks michael

 To: teamgrumman-list(at)matronics.com

Subject: Re: re:cowling update

Date: Tue C 16 Sep 2008 23:57:39 -0400

From: robsherwin(at)aol.com

The same is true of the AA5 (and AA5A) POH's.  The Tiger POH is much more realistic.  The high C and especially the high and hot C for the Cheetah's take distance get increasingly ridiculous.  Compare the take off distance over 50' at standard temp at 8 C000.  For the Cheetah C it's 2 C700 but for the Tiger it's about 3 C450.  How can that be?  The Cheetah takes longer at sea level to take off and has a significantly lower service ceiling.  There is no way that it is magically that much better than the Tiger just when it's high (and/or hot).  We all know that's when those of us that have 150 bhp wish for 160 (or more).

By the way C Gary C I now own Kevin Loftus 9853U (since '04).  She flies like a champ still (except for that density altitude thing).

Rob

--

JHOSLER(at)epri.com
Guest

Posted: Wed Sep 17, 2008 10:25 am Post subject: cowling update

With that kind of oil temp I would remove oil filter and  check for metal.

  

 John



   From:  owner-teamgrumman-list-server(at)matronics.com  [mailto:owner-teamgrumman-list-server(at)matronics.com] On Behalf Of Michael  Karatsonyi

Sent: Wednesday, September 17, 2008 2:05 PM

To:  teamgrumman-list(at)matronics.com

Subject: RE: TeamGrumman-List:  re:cowling update

 

hello all,

i have a 1978 grumman aa1-c with the original 0235 L2C  i am located in southern ca. my question is i recently flew with a passenger  with only using 365lbs of my 489 useful load minus 6-8 gal of gas. i departed  van nuys and slowly climbed to 2300' after about maybe 10 min of flight i  noticed oil temp was 290 or so ..close to yellow/red on gauge so i leveled out  full rich and pull rpm back to 2100rpm it slowly cooled but what i noticed and  what my question is ...is that cabin heat was off and vents full open(oh by the  way i had canopy open) it was 70 degrees outside nice and cool but vents were  blowing out hot air i verified and cycled cabin heat it got hotter shut it off  but still warm....does anyone anything about this...thanks michael

  

To: teamgrumman-list(at)matronics.com

Subject: Re:  re:cowling update

Date: Tue, 16 Sep 2008 23:57:39 -0400

From:  robsherwin(at)aol.com



The same is true of the AA5 (and AA5A) POH's.   The Tiger POH is much more realistic.  The high, and especially the high  and hot, for the Cheetah's take distance get increasingly ridiculous.   Compare the take off distance over 50' at standard temp at 8,000.  For the  Cheetah, it's 2,700 but for the Tiger it's about 3,450.  How can that  be?  The Cheetah takes longer at sea level to take off and has a  significantly lower service ceiling.  There is no way that it is magically  that much better than the Tiger just when it's high (and/or hot).  We all  know that's when those of us that have 150 bhp wish for 160 (or more).



By  the way, Gary, I now own Kevin Loftus 9853U (since '04).  She flies like a  champ still (except for that density altitude  thing).



Rob

--

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Thu Sep 18, 2008 10:10 pm Post subject: cowling update

I'm sorry, but, I don't understand the question(s?). Â  

 

  (1) What I understand is: Â You had hot air coming out of your fresh air vents with an OAT of 70 degrees. Â 

  

 

  (2) What I understand is: Â When you open the cabin heat, the air from the fresh air vents gets hotter. Â 

  

 

  (3)Â What I understand is: Â You were trying to climb a 2-seater at near gross weight with the canopy open.

  

 

  (4)Â What I understand is: Â Your average rate of climb to 2300 feet was 230 fpm.

  

 

  (5)Â What I understand is: Â You had oil temps at 290 degrees.

 

 

  =======

  

 

  (1) Check for a leak from your cowling

  (2) There is no connection between the cabin heat and fresh air unless someone has modified the ventilation system

  (3) Opening the canopy in flight increases parasitic drag. Â Climbing with it open is a sure way to get behind the power curve. Â Ask me how I know.Â 

  (4) You need some serious engine work.

  (5) You need some serious engine work. Â Then, install a quality digital oil temp sensor. Â By quality, I mean, don't buy a Westac or some other cheap, non-approved, instrument. Â 

  

 

  

 

  

 

  

 

  

 

 --

_________________
Gary
AuCountry Aviation
Home of Team Grumman

flyv35b(at)minetfiber.com
Guest

Posted: Fri Sep 19, 2008 5:02 am Post subject: cowling update

I'll add some comments to Gary's (shown  below)

  

 1.  The AA-1C POH says the plane should climb  ABOUT 700 fpm at 77 kts between SL and 2000 ft at 1500 lb and 68 F with the  cruise prop.

 2.  Opening the canopy greatly increases the drag  and there is no data for climb in that condition.  Needless to say the ROC  would suffer considerably.  Also the airflow around the cowling and  windshield likely changed such that hot air escaping from the engine compartment  was getting sucked into the NACA fresh air ducts.  This happens some anyhow  with air that leaks out the cowl latches.

 3.  290 F oil temp is way above the 245 F  redline!  What makes you say you had 290 F??  Even 245 F is very hot  for your ambient temp and the AA-1C which has an oil cooler, especially after  only 10 min.  Climbing at a slow speed with the canopy open most likely  adversely affects both oil and cylinder head temperatures.

 4.  If you don't have a good digital 4 cylinder  CHT instrument, I would buy one as you may be cooking your cylinders as  well.  Also at least check the accuracy of your oil temp instrument per the  maintenance manual or install a good digital instrument.

 5.  Don't climb with the canopy open if you want  decent ROC and don't want to cook your engine.  And climb at a high speed  than the POH says for best ROC, probably about 90 kts.

 6.  Check your cylinder compression to see what  the ring leakage is.  Excess blow-by past the rings will overheat the  oil.

  

 Cliff  A&P/IA

  

 (Original Post)

 hello all,

i have a 1978 grumman aa1-c with the original 0235 L2C i am  located in southern ca. my question is i recently flew with a passenger with  only using 365lbs of my 489 useful load minus 6-8 gal of gas. i departed van  nuys and slowly climbed to 2300' after about maybe 10 min of flight i noticed  oil temp was 290 or so ..close to yellow/red on gauge so i leveled out full rich  and pull rpm back to 2100rpm it slowly cooled but what i noticed and what my  question is ...is that cabin heat was off and vents full open(oh by the way i  had canopy open) it was 70 degrees outside nice and cool but vents were blowing  out hot air i verified and cycled cabin heat it got hotter shut it off but still  warm....does anyone anything about this...thanks michael



  

  	  Quote: 	
		     (Gary's Post)

   I'm sorry, but, I don't understand the question(s?).   

   



   (1) What I understand is:  You had hot air coming out of your fresh    air vents with an OAT of 70 degrees.  

   



   (2) What I understand is:  When you open the cabin heat, the air    from the fresh air vents gets hotter.  

   



   (3) What I understand is:  You were trying to climb a 2-seater    at near gross weight with the canopy open.

   



   (4) What I understand is:  Your average rate of climb to 2300    feet was 230 fpm.

   



   (5) What I understand is:  You had oil temps at 290    degrees.

   =======

   



   (1) Check for a leak from your cowling

   (2) There is no connection between the cabin heat and fresh air unless    someone has modified the ventilation system

   (3) Opening the canopy in flight increases parasitic drag.  Climbing    with it open is a sure way to get behind the power curve.  Ask me how I    know. 

   (4) You need some serious engine work.

   (5) You need some serious engine work.  Then, install a quality    digital oil temp sensor.  By quality, I mean, don't buy a Westac or some    other cheap, non-approved, instrument.  

	
Try     [quote][b]

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