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Bremspropeller
10-02-2008, 06:05 PM
Hey Crumpp,

some time ago I've read a pilot's account of a Schlachtflieger 190 pilot.
During transition somebody mentioned there were no diving restrictions to the airframe as such.

Now there's the challenge for you:
I know the a/c has a critical Mach (any published figure avaliable?), but Mcrit and flutter-speed do not always mix.

Relying on that account, the 190 could dive faster (though definately not advised..) than Mcrit - with limited to no elevator-control.

Now this is where another question kicks in:
The "all flying" tail (or trimmable stab) should give the pilot enough pitch-autority to recover from dives, even when flying faster than Mcrit.

Now if both applies, the 190 should have been quite safe in a dive (well, for a pilot who knows what the's doing...) and drag should be too high at some point for the airframe to overcome, thus limiting attainable dive-speed below fluttering-speed.


Is there any data to back up or smash this theory?

Thanks. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Bremspropeller
10-02-2008, 06:05 PM
Hey Crumpp,

some time ago I've read a pilot's account of a Schlachtflieger 190 pilot.
During transition somebody mentioned there were no diving restrictions to the airframe as such.

Now there's the challenge for you:
I know the a/c has a critical Mach (any published figure avaliable?), but Mcrit and flutter-speed do not always mix.

Relying on that account, the 190 could dive faster (though definately not advised..) than Mcrit - with limited to no elevator-control.

Now this is where another question kicks in:
The "all flying" tail (or trimmable stab) should give the pilot enough pitch-autority to recover from dives, even when flying faster than Mcrit.

Now if both applies, the 190 should have been quite safe in a dive (well, for a pilot who knows what the's doing...) and drag should be too high at some point for the airframe to overcome, thus limiting attainable dive-speed below fluttering-speed.


Is there any data to back up or smash this theory?

Thanks. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

CUJO_1970
10-02-2008, 08:13 PM
One thing is for sure:

If the FW190 carried a wallet, it would have "Badass Mother****er" engraved on it.

M_Gunz
10-02-2008, 08:32 PM
Before the P-38 there were lots of fighters with no dive restrictions.

Kettenhunde
10-02-2008, 08:37 PM
Smash it.

The q-limits of an airframe are hard limits.

The POH limits are set generally at the point risk of damage and are somewhat lower that the flutter limits. In affect all aircraft can exceed these limits. Doing so is the same as playing Russian roulette.


Anytime you exceed the limits you risk destruction as any damage weakens the aircraft. The margins on aircraft are small and the limits assume a perfect airframe. If you exceed them safely once, the airframe might very easily fail under much lower stresses.

http://www.youtube.com/watch?v=LPbhQS6IljU&feature=related

In fact structural failure can occur at speeds far below Vne. Exceeding Vno on a turbulent day can result in structural damage or failure.

All the best,

Crumpp

Viper2005_
10-02-2008, 09:14 PM
Eric Brown quotes the 190A as having a tactical Mach number of 0.75, and the 190D as having a tactical Mach number of 0.77.

Kettenhunde
10-02-2008, 09:19 PM
I wouldn't consider a Mach number from the 1940's as anything close to being accurate.

M_Gunz
10-03-2008, 04:47 AM
LOL, there were pre-WWII fighters that couldn't reach their own limits in dive.
And then came the P-38, first plane I know of to reach compression.
Perhaps that's because certain others were not dived for speed but rather only made level
speed records? Or possibly news of problems in those was held back or possibly they never
figured out why those few crashed? In the case of the Hughes racer there was a pilot error
problem, something loose.

DKoor
10-03-2008, 04:51 AM
Something tells me that pilots weren't exactly keen to test dive speed limits of their mounts.

Kocur_
10-03-2008, 05:00 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
And then came the P-38, first plane I know of to reach compression.
</div></BLOCKQUOTE>

Because it's unique airframe design 'invited' compression-related phenomenon at far lower speed than other fighters by speeding airflow over thick airfoil wings between fuselage and nacelles/booms - not because P-38 was so exceptionally fast.

Bremspropeller
10-03-2008, 05:21 AM
I dunno if I would compare a 190 with a utility a/c.

I have read the NTSB-report of that crash - the wings gave way because the pilot pulled 8Gs on an airframe that was designed for considerably less.

I've read the 190 reached an equivalent of 18Gs upon busting the airframe on a full-scale destructive test.

Structure-wise there should be lots of safety-margin (the a/c itself was only cleared for +/- 6G AFAIK) for the pilot.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">In fact structural failure can occur at speeds far below Vne. Exceeding Vno on a turbulent day can result in structural damage or failure. </div></BLOCKQUOTE>

I'm quite familiar with that.
The question is not if it was reasonable to do so, but if the airframe is capable of doing so.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The q-limits of an airframe are hard limits.

The POH limits are set generally at the point risk of damage and are somewhat lower that the flutter limits. </div></BLOCKQUOTE>

I've never heard a story of a 190 coming apart in mid-air.
That's in contrast to many other fighters of that age.

M_Gunz
10-03-2008, 05:41 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kocur_:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
And then came the P-38, first plane I know of to reach compression.
</div></BLOCKQUOTE>

Because it's unique airframe design 'invited' compression-related phenomenon at far lower speed than other fighters by speeding airflow over thick airfoil wings between fuselage and nacelles/booms - not because P-38 was so exceptionally fast. </div></BLOCKQUOTE>

I would compare it to the Hurricane.

Xiolablu3
10-03-2008, 05:54 AM
IMO the p38 was far more advanced than the Hurricane, just an opinion tho.

The olde Hurri was bascially just a Fury biplane with the top wing taken off. Also made in the old style of frame and fabric whereas the Spitfire, Me109 and P38 were true full metal monoplanes.

Bremspropeller
10-03-2008, 06:06 AM
The Hurricane also had a low Mcrit, that's what he's referring to.

HayateAce
10-03-2008, 07:02 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by CUJO_1970:
One thing is for sure:

If the FW190 carried a wallet, it would have "Badass Mother****er" engraved on it. </div></BLOCKQUOTE>

Urm, why would a fighter aircraft "carry" a "wallet?"


Curious in Chicago,

HYA

Bremspropeller
10-03-2008, 07:26 AM
So your fighter doesn't? http://forums.ubi.com/images/smilies/blink.gif

Viper2005_
10-03-2008, 08:14 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by HayateAce:
Urm, why would a fighter aircraft "carry" a "wallet?"


Curious in Chicago,

HYA </div></BLOCKQUOTE>

In the case of the P-47, obviously to store millions of dollars en-route to the nearest fly-in burger joint...

M_Gunz
10-03-2008, 11:32 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
The Hurricane also had a low Mcrit, that's what he's referring to. </div></BLOCKQUOTE>

Stories I remember about the P-38 were that older fighters could dive freely and not reach
limits so they were puzzled at first when the P-38s went augur.

I know it to be true of so many biplanes, they couldn't dive fast enough to get in trouble.

Could the Hurricane hit it's own critical Mach? Were those stories exaggerations and BS?

K_Freddie
10-03-2008, 12:14 PM
There is a WW2, record of an ex Junkers (not sure which type) pilot that put a FW into an 'all or nothing powered dive' on the eastern front, to prove a point. The plane reached 'terminal velocity' intact except for a few rivets here and there, and the exit from the dive was as easy as normal elevator controls, but slightly heavier.

Otherwise both pilot and plane flew another day.
http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

stalkervision
10-03-2008, 02:59 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by K_Freddie:
There is a WW2, record of an ex Junkers (not sure which type) pilot that put a FW into an 'all or nothing powered dive' on the eastern front, to prove a point. The plane reached 'terminal velocity' intact except for a few rivets here and there, and the exit from the dive was as easy as normal elevator controls, but slightly heavier.

Otherwise both pilot and plane flew another day.
http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif </div></BLOCKQUOTE>

I can believe it. The 190 is built like a tank.

M_Gunz
10-03-2008, 05:24 PM
Somehow I don't think that we'd be reading the stories from those who didn't make it.

Kettenhunde
10-03-2008, 05:30 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Structure-wise there should be lots of safety-margin (the a/c itself was only cleared for +/- 6G AFAIK) for the pilot.

</div></BLOCKQUOTE>

The average margin is ~1.5 for aircraft. That is for a symmetrical application as well. Asymmetrical loads greatly reduce the margin.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Sec. 25.303 Factor of safety.

Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified.

</div></BLOCKQUOTE>

http://adg.stanford.edu/aa241/structures/FAR301.html

I have heard of plenty of anecdotes of FW190's breaking up just as all airframes will do if the flutter limits are reached.

When I get back I will post some of the documents.

I don't understand, why even ask for my information if you are only going to dispute it?

All the best,

Crumpp

Bremspropeller
10-03-2008, 05:41 PM
I'm not disputing anything.

Are there any documents upon the a/c's limitations?

Would be nice to have a V,n-diagram.
But I guess there is none around.

Kettenhunde
10-03-2008, 09:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Are there any documents upon the a/c's limitations?
</div></BLOCKQUOTE>

Yes, the limits are published by Focke Wulf. I will post them for you when I am finished traveling.

All the best,

Crumpp

M_Gunz
10-03-2008, 09:43 PM
Safe Journey, C.

K_Freddie
10-04-2008, 01:09 AM
I think you should take the spec limits with a 'pinch of salt'.. They're usually recommended safety margins to ensure the a/c lasts it's design lifetime, but there's nothing to stop you trying to break it sooner.

I went to a local Korea Vets talk, where these guys explained that they were regularly pulling 9-Gs in a P51, and the one guy would pull 12-Gs.
The P51 had a G-meter.

So yes, continued abuse like this would eventually cause structural failure - something similar to buying a car. A second hand car driven by a granny would most likely be the best buy. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Bremspropeller
10-04-2008, 06:28 AM
Safe journey http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Freddie, it's also a matter of grossweight.
A fueled-up P-51 will propably not take the same load as an almost-empty one.