Questioning Dean's 3G stall data

[Sable]

I'm sure a number of you have "America's Hundred Thousand" by Francis Dean.  This is sort of a combined criticism/question.

My criticism is that the 3G stall speeds that Francis Dean lists in there, and that we all know and love are totally inaccurate.  His source for that data was the USN joint fighter conference.  If you take a look at the cards at the end of the report from the conference, you can see the measured 3G stall speeds(as well as the clean stall etc.), and no information is given as to the load condition of the aircraft, if any flaps were used etc.  When you look at the numbers they came up with(ranges of 10-20mph for 1G stall, and often 30-40+mph for 3G stall) it's obvious that the aircraft were being tested at different loads, and with different flap settings etc.

Now I know that we can simply look at the pilots manual for these planes, pick the clean stall speed(which almost always lists the aircraft load), determine the CLmax, and then determine the 3G stall.  But that only works for a clean condition, as stall speeds using flaps are almost never listed in pilot's manuals.  Does anyone know where I could find this data?  For some aircraft, this is pretty vital to accurately simulating their performance(P-38 and P-51 for example both had a manuever flap setting) I've been digging through the NACA report server, but I've had no luck in finding any actual tests of WWII aircraft in a flapped condition.  Anybody have any primary sources on this?  Thanks!

Sable
352nd FG

[Widewing]

 

Originally posted by Sable:
I'm sure a number of you have "America's Hundred Thousand" by Francis Dean.  This is sort of a combined criticism/question.

My criticism is that the 3G stall speeds that Francis Dean lists in there, and that we all know and love are totally inaccurate.  His source for that data was the USN joint fighter conference.  If you take a look at the cards at the end of the report from the conference, you can see the measured 3G stall speeds(as well as the clean stall etc.), and no information is given as to the load condition of the aircraft, if any flaps were used etc.  When you look at the numbers they came up with(ranges of 10-20mph for 1G stall, and often 30-40+mph for 3G stall) it's obvious that the aircraft were being tested at different loads, and with different flap settings etc.

Now I know that we can simply look at the pilots manual for these planes, pick the clean stall speed(which almost always lists the aircraft load), determine the CLmax, and then determine the 3G stall.  But that only works for a clean condition, as stall speeds using flaps are almost never listed in pilot's manuals.  Does anyone know where I could find this data?  For some aircraft, this is pretty vital to accurately simulating their performance(P-38 and P-51 for example both had a manuever flap setting) I've been digging through the NACA report server, but I've had no luck in finding any actual tests of WWII aircraft in a flapped condition.  Anybody have any primary sources on this?  Thanks!

Sable
352nd FG

Turn to page 603 in America's 100K and take a look at the table. It specifically states that the aircraft did not use flaps and provides a gross weight for each.

The P-38L manual provides the following stall data (I hope this formats properly):

                 Power Off
Weight:      15,000     17,000     19,000
Clean:         94 mph     100 mph    105 mph
Gear and
flaps down: 69 mph     74 mph     78 mph

My regards,

Widewing


[This message has been edited by Widewing (edited 03-23-2001).]

[Sable]

Yes, but for instance Dean lists the P-51D's 3G stall at 159mph, at 9500lbs.  If this were clean then that would mean that the P-51's wing had a CLmax of 1.89, and would yield a stall speed at 10,200(combat takeoff weight) of 93mph clean.  A quick check of the P-51 manual shows a stall of 106mph at this load, and NACA wind tunnel tests of the wing verify that this should be correct.

Furthermore, if you look at the text of the report (which is his source)there is no information on what condition or load any of the planes were at.  Moreover 159mph wasn't necessarily a data point recorded for the P-51 ... simply an average of the results that were found!


Sable
352nd FG

[wells]

The results are all over the map and include propwash effects, instrument errors at high angles of attack and or varying slip/skid angles in the turn, different pilots, etc.

[Sable]

The question still stands ... are there any good record for the level 1G stall for any of these planes using their flaps?

Sable
352nd FG

[GRUNHERZ]

What the US pilots uber FM bible might be incorrect? No way, you must be muted or better yet shot!   hehe

[Moss]

I don't usually put anything in here because I don't know enuff but I DO know that stall occurs at different speeds at different altitudes.  Sooo..what altitude were these tests done at?

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Moss

[Sable]

In theory, that shouldn't really matter ... stall speed is measured in IAS.  The reduction in indicated airspeed occurs at the same rate as the increase in stall speed because they are affected by the same thing - the thinning of the air.(at least thats my understanding)

Sable
352nd FG


 

Originally posted by Moss:
I don't usually put anything in here because I don't know enuff but I DO know that stall occurs at different speeds at different altitudes.  Sooo..what altitude were these tests done at?

[Widewing]

 

Originally posted by Sable:
The question still stands ... are there any good record for the level 1G stall for any of these planes using their flaps?

Sable
352nd FG

Power on or power off? It makes a difference.

My regards,

Widewing

[Sable]

I'd be interested in seeing any and all data available, power on or off!  

Sable
352nd FG

[wells]

Sable,

The flight manual for the plane in question is probably the best source, since it gives power on, power off, with flaps and gear down or up and instrument error at various speeds.  

[Sable]

I have a few of these, but unfortunatly they just give clean and landing configuration.  This leaves me wondering about planes like the P-51, F4U, or P-38 which developed their best turning performance using a manuevering flap setting.  I'm getting the feeling that this data just doesn't exist.  

Sable
352nd FG

[F4UDOA]

Sable,

Your right, that info probable doesn't exist. However if your lucky maybe Zigrat or Wells can find a way to incorperate that data into there spreadsheets.

BTW, the flaps in AH don't produce nearly enough lift. So don't bother trying to test this on our planeset. You will never get the full flapped landing configurations stalls to match AH.

[Daff]

As a general rule of thumb, the 2G stall speed is about 50% higher than the 1G stall speed...so 159mph at 3Gs might even be too generous!....it certainly does not sound too high.

Daff

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CO, 56th Fighter Group
 www.56thfightergroup.org
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