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Author Topic: 109 Flaps  (Read 8985 times)

Offline Charge

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« Reply #180 on: February 01, 2006, 06:40:16 AM »
Yes it is. it is surely good for high speed flying because of its thinness. Do you know how a thin wing handles AoA?

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Offline Angus

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« Reply #181 on: February 01, 2006, 08:57:10 AM »
What's that got to do with it?
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It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Crumpp

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« Reply #182 on: February 01, 2006, 10:26:44 AM »
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What's that got to do with it?


Umm...recovery perhaps?

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There is ABSOLUTELY NOTHING to substantiate this "claim" in the NACA documents you linked.


Sure there is, read the reports from 1/2 decade AFTER the war.  Even then the margin of error above mach .8 is substantial.

I posted these reports to show that post war we where still struggling with transonic realm speed measurement.

Most of today's fighters place the pitot tube on the nose as this has been determined as the best location in order to reduce the margin of error in the transonic realm.

That does nothing though to solve the error's in other methods.  

All the best,

Crumpp
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Offline justin_g

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« Reply #183 on: February 01, 2006, 11:02:21 AM »
None of the error correction factors in those reports show any noticable change in trend over 0.8M.

Give me a link to any one page from those reports which shows or explains this supposed decrease in accuracy over 0.8M... I don't see it.
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Offline Charge

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« Reply #184 on: February 01, 2006, 02:01:11 PM »
"Umm...recovery perhaps?"

I'd say that in case of Spitfire the wing planform affects most the final stages of stall and probably recovery too, but it is all about the profile and its effects on max allowable AoA before you get to the effects of planform ie. the lift distribution along the span.

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Offline Widewing

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« Reply #185 on: February 01, 2006, 04:52:19 PM »
I won't comment of the dive speeds reported for Spitfires as I have not looked at any of the test documents. However, I do have a lot of test data from dive testing of a P-47D-30 performed in 1949. Curtiss Wright was exploring propeller designs that would retain a higher degree of efficiency at high Mach. Test pilot Herb Fisher flew the entire test series, making as many as 10 dives a day. The P-47 below (by then redesignated as the F-47) attained a maximum speed of Mach 0.83 during the second dive test of 10/27/49.



This Jug had been retro-fitted with dive recovery flaps, but Fisher pulled the circuit breaker and didn't use them. The under wing stores pylons had been removed to reduce drag.

I have several data sheets graphing dive performance of some of these flights and the one below represents Fisher's 6th dive of that day.



Fisher attained Mach 0.79 during this dive.

Before he was done with the test program, Fisher made over 200 dives, all of which exceeded the AAF placcarded limits by a considerable margin. Fisher even brought along his 3 year-old son on one flight, where he attained Mach 0.78, no doubt making Herb Jr. the fastest toddler on earth for some years to come. Herb Jr wrote me and said, "I do not know if you have seen the “fastest toddler” picture, well the story is true. Here's a photo."



Anyway, my point is this: Fisher's P-47 was fitted with all manner of data recording hardware, including a mach meter and a specilized pitot tube engineered for accuracy at transonic speeds. His airspeed was also measured with a ground based radar theodolite operated by NACA personnel (identical to that which verified Yeager's flights in the XS-1). They had redundant data sources to verify speeds attained.

Fisher wrote that as he reached Mach 0.80, the aircraft began to experience a severe vibration and the torque meter monitoring the prop shaft began to display a marked oscillation in torque. At Mach 0.83 the aircraft ceased accelerating and the torque meter indicated wild fluctuations. Fisher was quite concerned that the prop shaft might fail. Upon landing, an inspection revealed no apparent damage. Fisher flew the balance of the scheduled dives, but with a Mach 0.80 limit due to the very real risk of throwing the propeller under the extreme stresses of the monumental drag rise.

My understanding is that the Spitfire reported to have reached Mach 0.9 did so AFTER the prop shaft had failed and thrown the prop, thus eliminating a significant drag factor.

My regards,

Widewing
« Last Edit: February 01, 2006, 05:02:30 PM by Widewing »
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My regards,

Widewing

YGBSM. Retired Member of Aces High Trainer Corps, Past President of the DFC, retired from flying as Tredlite.

Offline Angus

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« Reply #186 on: February 01, 2006, 06:23:28 PM »
Widewing Rules!
Would be nice to see more on that.
Anyway, it would not be the wings altogether, well, not the thickness. The Spitty's high speed elevator authority comes (I belive) from the positions. So, it's not the ellipse, nor aspect ratio, nor precisely the thickness that rules that party.
Well, my 2 cents.
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It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Crumpp

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« Reply #187 on: February 01, 2006, 06:49:34 PM »
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The Spitty's high speed elevator authority comes (I belive) from the positions.


What does that have to do with diving ability?  Other than putting the pilot and aircraft at risk?

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Crumpp says:
They measured mach .85 but that does NOT mean the aircraft achieved it. It's doubtful simply due to the fact the plane has that big propeller disc on the front!


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Fisher flew the balance of the scheduled dives, but with a Mach 0.80 limit due to the very real risk of throwing the propeller under the extreme stresses of the monumental drag rise.


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My understanding is that the Spitfire reported to have reached Mach 0.9 did so AFTER the prop shaft had failed and thrown the prop, thus eliminating a significant drag factor.


All the best,

Crumpp
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Offline Angus

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« Reply #188 on: February 01, 2006, 08:04:10 PM »
Crumpp:
"--------------------------------------------------------------------------------
The Spitty's high speed elevator authority comes (I belive) from the positions.
--------------------------------------------------------------------------------



What does that have to do with diving ability? Other than putting the pilot and aircraft at risk?"

Well, for starters, giving him the option of recovering from an insane dive instead of becoming fertilizer for further generations. It's less risky being able to recover than not....
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It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Crumpp

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« Reply #189 on: February 01, 2006, 11:00:59 PM »
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Well, for starters, giving him the option of recovering from an insane dive instead of becoming fertilizer for further generations. It's less risky being able to recover than not....


Only a handful of aircraft compressed to the point of no recovery.  Almost all had higher stick force per G at high speed purposely designed in to preserve both the pilot and plane.

I posted that page from Perkins & Hage and I know you have seen it.

That prevents overloading.  I have some pictures of overloaded Spitfires along with the reconstruction's of how they broke up in flight.

Additionally stick force per G is very much altitude and CG dependant and can vary over a very large range.

Having "light" elevator forces at high speed is not a feature, it's a flaw.

All the best,

Crumpp
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Offline Angus

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« Reply #190 on: February 02, 2006, 03:35:43 AM »
" I have some pictures of overloaded Spitfires along with the reconstruction's of how they broke up in flight. "

Other than the Mk V? They were doing quite a bit of it for a while, I am pretty sure you have seen on the boards why exactly that was, and how that was countered.
Oh, how did you like the Hurri pilots tale? Well, he just happened to survive to tell the tale, and adding on to that, he claimed this would not have happened to him in a Spit.

And the page you mention, I may have seen it, it just doesn't come to mind right away, so gimme a hand and point at it will you :)
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It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Angus

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« Reply #191 on: February 03, 2006, 10:54:20 AM »
Could you give something on those pics? Are they not mostly Mk V's?
Anyway, since the "removal" of the prop apparently kept the aircraft bashing on untill that famous number, it indicates 3 things:
1. Elevator still works at THAT insane speed.
2. Structure is pretty solid.
3. The limiting factor to the divespeed is the prop itself. (Crumpp being very spot on about that, - hadn't crossed my mind it could be the prop itself, but explains a lot)

so? A wee more of the elevator stuff?
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It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Crumpp

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« Reply #192 on: February 03, 2006, 12:24:14 PM »
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Anyway, since the "removal" of the prop apparently kept the aircraft bashing on untill that famous number, it indicates 3 things:


You think there is anything useful performance wise to be gained after that point?
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Offline Guppy35

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« Reply #193 on: February 03, 2006, 12:52:51 PM »
Image of the Spit in question.  It was a Spitfire PRXI which had none of the lumps and bumps on the wings of the fighter versions so it was a much cleaner wing.

Flight was April 27, 1944 a Farnborough and the plane was fitted with special recording gear for the high speed dive tests.  According to the pilot the prop came off AFTER he'd passed the highest speeds.

He recorded a true airspeed of 606 mph or .89 mach.

This from Alfred Price's  book  "The Spitfire Story"

Not gonna argue about it either way as frankly I don't care :)

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Offline Angus

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« Reply #194 on: February 03, 2006, 01:25:52 PM »
Guppy, as ever :)

Crumpp:
"You think there is anything useful performance wise to be gained after that point?"
Performance wise, yes perhaps, if the prop would be the stopping part.
Anyway:

It shows that the wing was not the "stopper". The airframe didn't stop it.
If Guppy's quote is right, not even the prop is the stopper.  It has been shown that the measurements were ok.
And you needed good G tolerance and elevator authority to get out of a crazy dive like that.
So, Crumpp, many factors determine the top diving speed, and I'll stick to my claim that the recordbreaker is probably somewhere 30 ft underground, - in a 109, 190, P47, P51 or whatever.

Oh, as a sidenote, - 606 TAS is how much IAS at 20K?
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It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)
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