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Whirl Wind Prop

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k7wx

Joined: 24 May 2010
Posts: 117

Posted: Mon Jan 17, 2011 6:18 pm Post subject: Whirl Wind Prop

Oliver,



Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first time on Saturday. Some observations...



  •  Performance is very good in the climb. 



  •  Not a surprise, there is drag at reduced power / RPM. Landing required some power to maintain airspeed. No problem, just different. 



  •  May require some hub changes. When Bill Blackwell did the first test flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and Carl will chase this for me. 



Initial experience is very positive. Here is a picture with the airplane now back in my hanger at FFZ.



Warren Hill

N464TW



On Dec 6, 2010, at 1:03 AM, ssssskippy wrote:



 	  Quote: 	
		   

 

 Hi All

 

 Some Pireps for this wonderfull whirlwind prop?

 

 Bye

 

 Olivier

 

 -----Message d'origine-----

 De : owner-yak-list-server(at)matronics.com

 [mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

 Envoyé : jeudi 18 novembre 2010 14:45

 À : yak-list(at)matronics.com

 Objet : Re: Whirl Wind Prop

 

 Doug,

 

 I have blade serial numbers 001 and 002 of this prop design and should have

 it on my CJ-6A with a M-14P within a couple of weeks. Will let you know how

 it performs. Attached is a picture from WhirlWind of the V-530WT on a Yak-52

 while the design was being evaluated. 

 

 Jill Gernetzke did an absolutely beautiful job of mounting my blades on an

 overhauled V-530 hub with a static balance. She is an artist. 

 

 Warren Hill

 Mesa, AZ

 N464TW

IMG_0286.jpg

Description:

Filesize:

1.77 MB

Viewed:

9723 Time(s)

ssssskippy

Joined: 02 May 2010
Posts: 58

Posted: Tue Jan 18, 2011 12:39 am Post subject: Whirl Wind Prop

Thanks!!



Olivier



-----Message d'origine-----

De : owner-yak-list-server(at)matronics.com

[mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

Envoyé : mardi 18 janvier 2011 03:13

À : yak-list(at)matronics.com

Objet : Re: Whirl Wind Prop



Oliver,



Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

time on Saturday. Some observations...



  •  Performance is very good in the climb. 



  •  Not a surprise, there is drag at reduced power / RPM. Landing required

some power to maintain airspeed. No problem, just different. 



  •  May require some hub changes. When Bill Blackwell did the first test

flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

Carl will chase this for me. 



Initial experience is very positive. Here is a picture with the airplane now

back in my hanger at FFZ.



Warren Hill

N464TW

ssssskippy

Joined: 02 May 2010
Posts: 58

Posted: Tue Jan 18, 2011 1:39 am Post subject: Whirl Wind Prop

Just an other question:



Did you notice a real improvement of the cruising speed? any numbers?



Thanks



Olivier



-----Message d'origine-----

De : owner-yak-list-server(at)matronics.com

[mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

Envoyé : mardi 18 janvier 2011 03:13

À : yak-list(at)matronics.com

Objet : Re: Whirl Wind Prop



Oliver,



Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

time on Saturday. Some observations...



  •  Performance is very good in the climb. 



  •  Not a surprise, there is drag at reduced power / RPM. Landing required

some power to maintain airspeed. No problem, just different. 



  •  May require some hub changes. When Bill Blackwell did the first test

flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

Carl will chase this for me. 



Initial experience is very positive. Here is a picture with the airplane now

back in my hanger at FFZ.



Warren Hill

N464TW

k7wx

Joined: 24 May 2010
Posts: 117

Posted: Tue Jan 18, 2011 6:38 am Post subject: Whirl Wind Prop

Theoretically, this should perform well as a cruise prop. So far, have done only one short airport-to-airport flight. Seemed to need about 600 mm manifold pressure with RPM at 82% for 120 to 140 KIAS. Will let you know the stable settings and airspeed after a cross country flight towards the end of the month.



On Jan 18, 2011, at 2:37 AM, ssssskippy wrote:



 	  Quote: 	
		   

 

 Just an other question:

 

 Did you notice a real improvement of the cruising speed? any numbers?

 

 Thanks

 

 Olivier

 

 -----Message d'origine-----

 De : owner-yak-list-server(at)matronics.com

 [mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

 Envoyé : mardi 18 janvier 2011 03:13

 À : yak-list(at)matronics.com

 Objet : Re: Whirl Wind Prop

 

 Oliver,

 

 Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

 time on Saturday. Some observations...

 

  •  Performance is very good in the climb. 

 

  •  Not a surprise, there is drag at reduced power / RPM. Landing required

 some power to maintain airspeed. No problem, just different. 

 

  •  May require some hub changes. When Bill Blackwell did the first test

 flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

 Carl will chase this for me. 

 

 Initial experience is very positive. Here is a picture with the airplane now

 back in my hanger at FFZ.

 

 Warren Hill

 N464TW

Dale

Joined: 30 May 2007
Posts: 178

Posted: Tue Jan 18, 2011 7:23 am Post subject: Re: Whirl Wind Prop

As propeller disk size increases the static thrust increases.

As the disk size increases so does drag. 

Static thrust does not directly relate to higher cruise speed.

Static thrust does increase climb performance at the cost of higher cruise speed with large dia props. Go faster add more blades and reduce dia.

No free ride.  MT says that the blade shape has little to do with performance between their straight blade or curved blade.

It just depends on what you like to look at. Sikorsky developed a

variable dia rotor system for the tilt rotor that demonstrates this 

in a way over the top example.  It increases the cruise speed as the 

rotors are retracted and disk drag decreases.

viperdoc(at)mindspring.co
Guest

Posted: Tue Jan 18, 2011 8:03 am Post subject: Whirl Wind Prop

Just an observation since I'm not a CJ kinda guy but flying under square vs over square is costing you in performance. If you are setting pitch at 82% you should have your manifold pressure at 82 to 85% depending on altitude for the single stage super charger. What are the nominal prop and manifold settings for the CJ from the handbook? I thought CJs reported prop revolutions as RPM not %RPM? I do not have my YAK 52 pilots handbook at hand currently to quote verbatim from but... I use nominal 1 settings for best economy as 60-62% pitch and 60 -65% manifold pressure. Square would be 60-62% and 60-62mmHg. Nominal 2 is 64% and 65 mmHg in the RU manual as I memorized. Over square would be 64% RPM and 70%. at higher manifold pressures you have the engine pushing the prop not the prop pulling the engine AT high Rpm but low manifold pressure. You are akin to putting the car in second gear to climb a hill but giving it little gas by not mashing the accelerator so the engine loads up and stalls. If you  increase mmHg (manifold pressure) to square 8o% and 800 mmHg I think your cruise speeds at the higher performance power setting  will improve to around 160-170 it's range. 

Now maybe I've just committed mental masturbation here if the initial post was a typo. 600 mm manifold was really 800 mm.???

Doc

Sent from my iPad

On Jan 18, 2011, at 8:35 AM, Warren Hill <k7wx(at)earthlink.net> wrote:

 	  Quote: 	

 Theoretically, this should perform well as a cruise prop. So far, have done only one short airport-to-airport flight. Seemed to need about 600 mm manifold pressure with RPM at 82% for 120 to 140 KIAS. Will let you know the stable settings and airspeed after a cross country flight towards the end of the month.

 On Jan 18, 2011, at 2:37 AM, ssssskippy wrote:

> 

> 

> Just an other question:

> 

> Did you notice a real improvement of the cruising speed? any numbers?

> 

> Thanks

> 

> Olivier

> 

> -----Message d'origine-----

> De : owner-yak-list-server(at)matronics.com

> [mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

> EnvoyÃ© : mardi 18 janvier 2011 03:13

> Ã€ : yak-list(at)matronics.com

> Objet : Re: Whirl Wind Prop

> 

> Oliver,

> 

> Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

> time on Saturday. Some observations...

> 

> â€¢  Performance is very good in the climb. 

> 

> â€¢  Not a surprise, there is drag at reduced power / RPM. Landing required

> some power to maintain airspeed. No problem, just different. 

> 

> â€¢  May require some hub changes. When Bill Blackwell did the first test

> flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

> Carl will chase this for me. 

> 

> Initial experience is very positive. Here is a picture with the airplane now

> back in my hanger at FFZ.

> 

> Warren Hill

> N464TW

> 

> 

> 

> 

> 

> 

> 

>

k7wx

Joined: 24 May 2010
Posts: 117

Posted: Tue Jan 18, 2011 8:56 am Post subject: Whirl Wind Prop

Doc,

This flight was not a good test. Just from DVT to FFZ and in formation with another CJ and a T6... with purposely slower indicated airspeeds. As such the MP was all over the place for station keeping. Need to take a bone fide cross flight to better appreciate the performance. Will do this on the 29th up to Kingman to visit Jill and Carl. 

Also, was flying with a zero time M-14P which now has only about 1.5 hours. Still need to do a break in. 

Lots going on. 

Warren

On Jan 18, 2011, at 8:56 AM, Roger Kemp M.D. wrote:

 	  Quote: 	

 Just an observation since I'm not a CJ kinda guy but flying under square vs over square is costing you in performance. If you are setting pitch at 82% you should have your manifold pressure at 82 to 85% depending on altitude for the single stage super charger. What are the nominal prop and manifold settings for the CJ from the handbook? I thought CJs reported prop revolutions as RPM not %RPM? I do not have my YAK 52 pilots handbook at hand currently to quote verbatim from but... I use nominal 1 settings for best economy as 60-62% pitch and 60 -65% manifold pressure. Square would be 60-62% and 60-62mmHg. Nominal 2 is 64% and 65 mmHg in the RU manual as I memorized. Over square would be 64% RPM and 70%. at higher manifold pressures you have the engine pushing the prop not the prop pulling the engine AT high Rpm but low manifold pressure. You are akin to putting the car in second gear to climb a hill but giving it little gas by not mashing the accelerator so the engine loads up!

  and stalls. If you  increase mmHg (manifold pressure) to square 8o% and 800 mmHg I think your cruise speeds at the higher performance power setting  will improve to around 160-170 it's range. 

 Now maybe I've just committed mental masturbation here if the initial post was a typo. 600 mm manifold was really 800 mm.???

 Doc

 Sent from my iPad

 On Jan 18, 2011, at 8:35 AM, Warren Hill <k7wx(at)earthlink.net> wrote:

> 

> 

> Theoretically, this should perform well as a cruise prop. So far, have done only one short airport-to-airport flight. Seemed to need about 600 mm manifold pressure with RPM at 82% for 120 to 140 KIAS. Will let you know the stable settings and airspeed after a cross country flight towards the end of the month.

> 

> On Jan 18, 2011, at 2:37 AM, ssssskippy wrote:

> 

>> 

>> 

>> Just an other question:

>> 

>> Did you notice a real improvement of the cruising speed? any numbers?

>> 

>> Thanks

>> 

>> Olivier

>> 

>> -----Message d'origine-----

>> De : owner-yak-list-server(at)matronics.com

>> [mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

>> Envoyé : mardi 18 janvier 2011 03:13

>> À : yak-list(at)matronics.com

>> Objet : Re: Whirl Wind Prop

>> 

>> Oliver,

>> 

>> Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

>> time on Saturday. Some observations...

>> 

>> •  Performance is very good in the climb. 

>> 

>> •  Not a surprise, there is drag at reduced power / RPM. Landing required

>> some power to maintain airspeed. No problem, just different. 

>> 

>> •  May require some hub changes. When Bill Blackwell did the first test

>> flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

>> Carl will chase this for me. 

>> 

>> Initial experience is very positive. Here is a picture with the airplane now

>> back in my hanger at FFZ.

>> 

>> Warren Hill

>> N464TW

>> 

>> 

>> 

>> 

>> 

>> 

>> 

>> 

> 

> 

> 

> 

> 

>

viperdoc(at)mindspring.co
Guest

Posted: Tue Jan 18, 2011 9:16 am Post subject: Whirl Wind Prop

Copy. Sounds like you are gonna have longterm fun.

Fly safe!

Doc



Sent from my iPad



On Jan 18, 2011, at 10:54 AM, Warren Hill <k7wx(at)earthlink.net> wrote:



 	  Quote: 	
		   

 

 Doc,

 

 This flight was not a good test. Just from DVT to FFZ and in formation with another CJ and a T6... with purposely slower indicated airspeeds. As such the MP was all over the place for station keeping. Need to take a bone fide cross flight to better appreciate the performance. Will do this on the 29th up to Kingman to visit Jill and Carl. 

 

 Also, was flying with a zero time M-14P which now has only about 1.5 hours. Still need to do a break in. 

 

 Lots going on. 

 

 Warren

 

 

 

 On Jan 18, 2011, at 8:56 AM, Roger Kemp M.D. wrote:

 

> 

> 

> Just an observation since I'm not a CJ kinda guy but flying under square vs over square is costing you in performance. If you are setting pitch at 82% you should have your manifold pressure at 82 to 85% depending on altitude for the single stage super charger. What are the nominal prop and manifold settings for the CJ from the handbook? I thought CJs reported prop revolutions as RPM not %RPM? I do not have my YAK 52 pilots handbook at hand currently to quote verbatim from but... I use nominal 1 settings for best economy as 60-62% pitch and 60 -65% manifold pressure. Square would be 60-62% and 60-62mmHg. Nominal 2 is 64% and 65 mmHg in the RU manual as I memorized. Over square would be 64% RPM and 70%. at higher manifold pressures you have the engine pushing the prop not the prop pulling the engine AT high Rpm but low manifold pressure. You are akin to putting the car in second gear to climb a hill but giving it little gas by not mashing the accelerator so the engine loads !

 up!

> and stalls. If you  increase mmHg (manifold pressure) to square 8o% and 800 mmHg I think your cruise speeds at the higher performance power setting  will improve to around 160-170 it's range. 

> Now maybe I've just committed mental masturbation here if the initial post was a typo. 600 mm manifold was really 800 mm.???

> Doc

> 

> Sent from my iPad

> 

> On Jan 18, 2011, at 8:35 AM, Warren Hill <k7wx(at)earthlink.net> wrote:

> 

>> 

>> 

>> Theoretically, this should perform well as a cruise prop. So far, have done only one short airport-to-airport flight. Seemed to need about 600 mm manifold pressure with RPM at 82% for 120 to 140 KIAS. Will let you know the stable settings and airspeed after a cross country flight towards the end of the month.

>> 

>> On Jan 18, 2011, at 2:37 AM, ssssskippy wrote:

>> 

>>> 

>>> 

>>> Just an other question:

>>> 

>>> Did you notice a real improvement of the cruising speed? any numbers?

>>> 

>>> Thanks

>>> 

>>> Olivier

>>> 

>>> -----Message d'origine-----

>>> De : owner-yak-list-server(at)matronics.com

>>> [mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

>>> EnvoyÃ© : mardi 18 janvier 2011 03:13

>>> Ã€ : yak-list(at)matronics.com

>>> Objet : Re: Whirl Wind Prop

>>> 

>>> Oliver,

>>> 

>>> Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

>>> time on Saturday. Some observations...

>>> 

>>> â€¢  Performance is very good in the climb. 

>>> 

>>> â€¢  Not a surprise, there is drag at reduced power / RPM. Landing required

>>> some power to maintain airspeed. No problem, just different. 

>>> 

>>> â€¢  May require some hub changes. When Bill Blackwell did the first test

>>> flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

>>> Carl will chase this for me. 

>>> 

>>> Initial experience is very positive. Here is a picture with the airplane now

>>> back in my hanger at FFZ.

>>> 

>>> Warren Hill

>>> N464TW

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>> 

>> 

>> 

>> 

>> 

>> 

> 

> 

> 

> 

>

george(at)gesoco.com
Guest

Posted: Tue Jan 18, 2011 9:38 am Post subject: Whirl Wind Prop

Hey, I agree on the M14P settings, just be a little cautious with the word "square" . 620 mm is about 24 inches and 62% is about 1830 RPM. That would be considered as  "Over Square" by most "flat engine" pilots.



George Coy



--

k7wx

Joined: 24 May 2010
Posts: 117

Posted: Tue Jan 18, 2011 10:02 am Post subject: Whirl Wind Prop

Doc,



That's the hope. Once I do a proper break-in on the engine and fly this prop for a while, I'll have a better appreciation for the actual performance. Before this, I was flying the same airplane with the Housai-6 engine and Chinese metal blade. It will be fun to now be able to play with the grown-ups!



Warren

On Jan 18, 2011, at 10:13 AM, Roger Kemp M.D. wrote:



 	  Quote: 	
		   

 

 Copy. Sounds like you are gonna have longterm fun.

 Fly safe!

 Doc

 

 Sent from my iPad

 

 On Jan 18, 2011, at 10:54 AM, Warren Hill <k7wx(at)earthlink.net> wrote:

 

> 

> 

> Doc,

> 

> This flight was not a good test. Just from DVT to FFZ and in formation with another CJ and a T6... with purposely slower indicated airspeeds. As such the MP was all over the place for station keeping. Need to take a bone fide cross flight to better appreciate the performance. Will do this on the 29th up to Kingman to visit Jill and Carl. 

> 

> Also, was flying with a zero time M-14P which now has only about 1.5 hours. Still need to do a break in. 

> 

> Lots going on. 

> 

> Warren

> 

> 

> 

> On Jan 18, 2011, at 8:56 AM, Roger Kemp M.D. wrote:

> 

>> 

>> 

>> Just an observation since I'm not a CJ kinda guy but flying under square vs over square is costing you in performance. If you are setting pitch at 82% you should have your manifold pressure at 82 to 85% depending on altitude for the single stage super charger. What are the nominal prop and manifold settings for the CJ from the handbook? I thought CJs reported prop revolutions as RPM not %RPM? I do not have my YAK 52 pilots handbook at hand currently to quote verbatim from but... I use nominal 1 settings for best economy as 60-62% pitch and 60 -65% manifold pressure. Square would be 60-62% and 60-62mmHg. Nominal 2 is 64% and 65 mmHg in the RU manual as I memorized. Over square would be 64% RPM and 70%. at higher manifold pressures you have the engine pushing the prop not the prop pulling the engine AT high Rpm but low manifold pressure. You are akin to putting the car in second gear to climb a hill but giving it little gas by not mashing the accelerator so the engine loads!

  !

> up!

>> and stalls. If you  increase mmHg (manifold pressure) to square 8o% and 800 mmHg I think your cruise speeds at the higher performance power setting  will improve to around 160-170 it's range. 

>> Now maybe I've just committed mental masturbation here if the initial post was a typo. 600 mm manifold was really 800 mm.???

>> Doc

>> 

>> Sent from my iPad

>> 

>> On Jan 18, 2011, at 8:35 AM, Warren Hill <k7wx(at)earthlink.net> wrote:

>> 

>>> 

>>> 

>>> Theoretically, this should perform well as a cruise prop. So far, have done only one short airport-to-airport flight. Seemed to need about 600 mm manifold pressure with RPM at 82% for 120 to 140 KIAS. Will let you know the stable settings and airspeed after a cross country flight towards the end of the month.

>>> 

>>> On Jan 18, 2011, at 2:37 AM, ssssskippy wrote:

>>> 

>>>> 

>>>> 

>>>> Just an other question:

>>>> 

>>>> Did you notice a real improvement of the cruising speed? any numbers?

>>>> 

>>>> Thanks

>>>> 

>>>> Olivier

>>>> 

>>>> -----Message d'origine-----

>>>> De : owner-yak-list-server(at)matronics.com

>>>> [mailto:owner-yak-list-server(at)matronics.com] De la part de Warren Hill

>>>> Envoyé : mardi 18 janvier 2011 03:13

>>>> À : yak-list(at)matronics.com

>>>> Objet : Re: Whirl Wind Prop

>>>> 

>>>> Oliver,

>>>> 

>>>> Flew my CJ-6A with the new Whirl Wind V530-WT composite blades for the first

>>>> time on Saturday. Some observations...

>>>> 

>>>> •  Performance is very good in the climb. 

>>>> 

>>>> •  Not a surprise, there is drag at reduced power / RPM. Landing required

>>>> some power to maintain airspeed. No problem, just different. 

>>>> 

>>>> •  May require some hub changes. When Bill Blackwell did the first test

>>>> flight last week, RPMs jumped up past 160 KIAS. I noticed the same. Jill and

>>>> Carl will chase this for me. 

>>>> 

>>>> Initial experience is very positive. Here is a picture with the airplane now

>>>> back in my hanger at FFZ.

>>>> 

>>>> Warren Hill

>>>> N464TW

>>>> 

>>>> 

>>>> 

>>>> 

>>>> 

>>>> 

>>>> 

>>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>> 

>> 

>> 

>> 

>> 

> 

> 

> 

> 

> 

>

mark.bitterlich(at)navy.m
Guest

Posted: Tue Jan 18, 2011 10:04 am Post subject: Whirl Wind Prop

I know I should not comment... but... the Devil made me do it!   



George said: "That would be considered as  "Over Square" by most "flat engine" pilots."  GEORGE!  Ummm... my "flat engine" runs at 3400 RPM at 48 inches.  Just sayin......  Nice to know I am not an "average" flat engine kind of guy!    



Doc:  I never considered the engine to be "pushing" the prop.  Interesting concept really.  So you're saying that anytime I am "under square", the prop is pulling the engine?  So just exactly how does that work?  As in, how can the aircraft maintain level flight with that happening?     



So, .... if you took your YAK-50 to say....15,000 feet....  where would the RPM be, and what would the manifold pressure read, and just how in the heck did you GET there, being "under square" and all?  



It's just all too darn complicated!  



Mark Bitterlich

--

wlannon(at)persona.ca
Guest

Posted: Tue Jan 18, 2011 12:56 pm Post subject: Whirl Wind Prop

George makes an interesting point here.



I don't think using RPM in percentage and MP in metric units (and/or in 

percentage of max. allowable MP) is a valid method of establishing "square, 

under square or over square".

Radial engines (unlike typical flat engines) need to operate predominately 

over-square within the manufacturers limits.



For example the typical numbers for the P&W R1340 are as follows.



1. Take-off -  (max.)                   RPM  2250,  MP 36"

2. Climb (rated power)                         2200        32.5

3. Aerobatic                                         2000         28-30

4. Cruise                                              1900          27

                                                            1800          26

                                                            1750          25



All of these are substantially over square. If we look at the typical cruise 

of 1800 RPM and 26" (normally referred to as "18 - 26") and convert to 

percentage & metric :----------



1800 = 83%,  26" = 660 mm  then 83/66 = under sq.

                                         and  83/660  = wayover sq.

OR  using percentage of both numbers:--------

Max. MP = 36",  26" = 72%  -  83/72       = under sq.



For the Huosai the specified cruise 2 is 1950 RPM at 660 mm/hg OR 26". 

1950RPM and 26".  "19.5 -26" is nicely oversquare.

Not to say that a similar set of numbers could not be developed to utilize 

percentage RPM and metric MP but it would not be referenced in the accepted 

Western manner.



FWIW

Walt

---

psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Sat Feb 05, 2011 8:19 am Post subject: Re: Whirl Wind Prop

This over-square under-square stuff is just short hand for a rule of thumb that works with some engines and with some systems of units. There is nothing that says revs should be measured per minute (could be per sec or to be completely wild, in % of max RPM), and nothing to say manifold pressure should be in inches of mercury (could be in cm of cider). Always refer to the engine and aircraft docs. Repeating this under/over square stuff is either patronising or it's displaying ignorance. Either way, not helpful. As for this prop pushing the engine stuff and for the car analogies who is to say what is 2nd gear and what is a hill when it comes to the M14P? The engine manufacturer, again. So also not helpful. That the M14P %RPM figure and cmHg figures are similar in some engine running regimes is nothing but a happy accident of units.

_________________
Paul Beardsell
G-PYAK http://beardsell.com/flying/g-pyak
Yak-18T http://beardsell.com/flying/yak18t

wlannon(at)persona.ca
Guest

Posted: Sat Feb 05, 2011 9:43 am Post subject: Whirl Wind Prop

Agreed, every aircraft engine should be operated in accordance with the 

manufacturers instructions.  No question about that.

However, it appears you are suggesting that it is not helpful to understand 

the reasons for those instructions.



In this community there are many new owners who have never operated a radial 

engine, possibly never a variable pitch propellor or have any experience 

with a supercharged aircraft engine.

Most want to understand how these things work.



BTW:  It is mm/Hg not cm.



Walt



---

psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Sat Feb 05, 2011 10:54 am Post subject: Re: Whirl Wind Prop

I am unsure which of us trying to teach the other's grandmother to suck eggs. Whatever the unit is it is not mm/Hg. It would be mmHg. That or cmHg. And this refers to the height of the column in a mercury barometer. Hg is the chemical symbol for mercury. The height is either 760mm (millimetres) Hg or 76cm (centimetres) Hg at standard sea level atmospheric pressure. If you think it convenient to have to have a number closer to the %RPM of your engine then it is the cmHg figure you want. The manifold pressure gauge in my and other Yaks I've seen is calibrated in neither of those units, they are calibrated in dm (decimeters) Hg. The engine manual too: Cruise 1 is 64% engine speed at 7.35 dmHg (or cmHg/10).



As for the Morris Minor put-putting up a hill in top gear full throttle, as long as the term under or over square is not used, I'm happy.

_________________
Paul Beardsell
G-PYAK http://beardsell.com/flying/g-pyak
Yak-18T http://beardsell.com/flying/yak18t

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