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Afromike1
02-07-2009, 01:57 PM
Do any of the dive planes in IL2 have dive breaks in order to slow down a dive bomb?

Afromike1
02-07-2009, 01:57 PM
Do any of the dive planes in IL2 have dive breaks in order to slow down a dive bomb?

VW-IceFire
02-07-2009, 02:04 PM
Yes...

Ju-87 Stuka (all but the anti-tank version)
Pe-2 (all versions)
SBD (both 3 and 5)
P-38L (not for dive bombing so much as high speed attack runs)
D3A Val
F4U Corsair (landing gear extends in an unlocked position for the purposes of dive bombing - a real feature!)

Probably left out some.

mortoma
02-07-2009, 09:03 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VW-IceFire:
Yes...

Ju-87 Stuka (all but the anti-tank version)
Pe-2 (all versions)
SBD (both 3 and 5)
P-38L (not for dive bombing so much as high speed attack runs)
D3A Val
F4U Corsair (landing gear extends in an unlocked position for the purposes of dive bombing - a real feature!)

Probably left out some. </div></BLOCKQUOTE>I think the air brakes on the P-38 were more to help it overcome the high speed compressibility problems. Before they installed dive brakes, the 38 got into quickly control problems once it got to a certain speed.

VW-IceFire
02-07-2009, 10:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by mortoma:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VW-IceFire:
Yes...

Ju-87 Stuka (all but the anti-tank version)
Pe-2 (all versions)
SBD (both 3 and 5)
P-38L (not for dive bombing so much as high speed attack runs)
D3A Val
F4U Corsair (landing gear extends in an unlocked position for the purposes of dive bombing - a real feature!)

Probably left out some. </div></BLOCKQUOTE>I think the air brakes on the P-38 were more to help it overcome the high speed compressibility problems. Before they installed dive brakes, the 38 got into quickly control problems once it got to a certain speed. </div></BLOCKQUOTE>
Thats exactly why they were installed. The P-38 suffers from extreme compressibility problems so the breaks help slow the plane and allow for the control surfaces to regain their use.

BigKahuna_GS
02-08-2009, 02:40 PM
S!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Thats exactly why they were installed. The P-38 suffers from extreme compressibility problems so the breaks help slow the plane and allow for the control surfaces to regain their use. </div></BLOCKQUOTE>


That is not really correct.

The P38 flaps were dive recovery flaps (not dive brakes). The P47 and F8F Bearcat also had dive recovery flaps. These dive recovery flaps were not designed to have a "braking" effect but rather to redirect airflow so that the shock wave and resulting "wash out" effect on the elevator could be corrected allowing elevator control again. When deployed the pilot didn't
actualy have to pull back on the stick the dive recovery flaps would pitch the nose up 10-20degress

The problem was the P38 wing which had a high lift coeffcient would cause the air traveling over the top of the wing to reach mach 1 quickly at high altitude, high speed and steep dive angles. A resulting shock wave would form on the elevator washing out all elevator control.

During combat following a 109 or 190 in a split-s from a bomber stream at high altitude could bring this on as the air traveling over the top of the wing could reach mach 1 speeds rather quickly if the dive angle was too steep. Another problem was that at the onset of compressibility
a "tuck under" effet could also happen steepining the dive angle with total loss of elevator control. This would be terrifying to a new pilot.

Experienced P38 pilots above 25,000ft (pre-dive recovery flaps) would throttle back, reduce dive angle and use rudder/airleron manuevers to prevent the onset of compressibility. Below 20,000ft
and as the speed of sound increased as altitude decreased there was no compressiblity problems for the P38. If you read some of the combat reports from Bong & McGuire in the Pacific they routinely power dived in the P38 from 20,000ft.

Here is P38/P51 Ace Robin Olds describing what it was like to be in compressibility in a P38 while escorting B-17s over Germany. (no dive recovery flaps)

http://www.youtube.com/watch?v=LsrTx9heTug

Every WW2 aircraft suffered from compressibility. Depending on the aircraft design, altitude, speed, each had an impact on the onset of the effects of compressibility.

How compressibility is modeled in the IL2 P38 is completely wrong as it compressess at all altitudes and it is not based on altitude/mach. Also when the dive recovery flaps are deployed on all P38L models there is no elevator control while compressed, this is incorrect.

Here is a NACA technical read:

NACA Terminal Dive Speed for P38

http://history.nasa.gov/SP-4219/Chapter3.html

FROM ENGINEERING SCIENCE TO BIG SCIENCE 83

The general aeronautics community was suddenly awakened to the realities of the unknown flight regime in November 1941, when Lockheed test pilot Ralph Virden could not pull the new, high-performance P-38 out of a high-speed dive, and crashed. Virden was the first human fatality due to adverse compressibility effects, and the P-38, shown below, was the first airplane to Suffer from these effects. The P-38 exceeded its critical Mach number in an operational dive, and penetrated well into the regime of the compressibility burble at its terminal dive speed, as shown by the bar chart on page 80 .35 The problem encountered by Virden, and many other P-38 pilots at that time, was that beyond a certain speed in a dive, the elevator controls suddenly felt as if they were locked. And to make things worse, the tail suddenly produced more lift, pulling the P-38 into an even

http://history.nasa.gov/SP-4219/4219-083.jpg


Lockheed P-38, the first airplane to encounter severe compressibility problems.
35. This chart is taken from the figure on page 78 of the article by R. L. Foss, "From Propellers to Jets in Fighter Aircraft Design," in Jay D. Pinson, ed., Diamond Jubilee of Powered Flight: The Evolution of Aircrafeet Design (New York, NY: American Institute of Aeronautics and Astronautics, 1978), pp. 51-64.

http://history.nasa.gov/SP-4219/4219-084.jpg

http://history.nasa.gov/SP-4219/4219-084.jpg
Bar chart showing the magnitude of how much the P-38 penetrated the compressibility regime

steeper dive. This was called the "tuck-under" problem. It is important to note that the NACA soon solved this problem, using its expertise in compressibility effects. Although Lockheed consulted various aerodynamicists, including Theodore Von Kármán at Caltech, it turned out that John Stack at NACA Langley, with his accumulated experience in compressibility effects, was the only one to properly diagnose the problem. The wing of the P-38 lost lift when it encountered the compressibility burble. As a result, the downwash angle of the flow behind the wing was reduced. This in turn increased the effective angle of attack of the flow encountered by the horizontal tail, increasing the lift on the tail, and pitching the P-38 to a progressively steepening dive totally beyond the control of the pilot. Stack's solution was to place a special flap under the wing, to be employed only when these compressibility effects were encountered. The flap was not a conventional dive flap intended to reduce the speed. Rather, Stack's idea was to use the flap to maintain lift in the face of the compressibility burble, hence eliminating the change in the downwash angle, and therefore allowing the horizontal tail to function properly. This is a graphic example of how, in the early days of high-speed flight, the NACA compressibility research was found to be vital as real airplanes began to sneak up on Mach one.36

Indeed, it was time for real airplanes to be used to probe the mysteries of the unknown transonic gap. It was time for the high-speed research airplane to become a reality. The earliest concrete proposal along these lines was made by Ezra Kotcher, a senior instructor at the Army Air Corps Engineering School at Wright Field (a forerunner of today's Air Force Institute of Technology). Kotcher was a 1928 graduate of the University of California,



--------------------------------------------------------------------------------

36. The "tuck-under" problem, and its technical Solution, is described in John D. Anderson, Jr., Introduction to Flight (New York, NY. McGraw-Hill Book Co., 3rd ed., 1989), pp. 406-08.

AllorNothing117
02-12-2009, 04:05 PM
What a read! http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif Can't thank you enough. I realy cannot stand the Copressabiltiy modeling. I wish It was fixed! BOBSOW prehaps.

BigKahuna_GS
02-18-2009, 10:29 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">What a read! Can't thank you enough. I realy cannot stand the Copressabiltiy modeling. I wish It was fixed! BOBSOW prehaps. </div></BLOCKQUOTE>


Your Welcome ! http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

There is more about NACA scientist John Stack and compressibility (WWII fighters) over at the NASA web site.

deepo_HP
02-19-2009, 12:40 AM
hi kahuna,

in addition, compressibility-effets were not only a problem in WWII fighters, but already discussed in the mid-20s and shown in 1934, when the (still) worldrecord-holder for sea-based planes found it's restriction at 709km/h due to compressibility. glauert was probably the first to make mach.7 possible by his methods, described 1928, based on prandtl's algorhythms on thin airfoils.
the following volta-congress in 1935 (with prandtl, busemann, karman, jacobs and wieselsberger) about high-speed aerodynamics was centered around the topic of 'correction of compressibility-effects' - presenting the first design of supersonic windchannel, new airfoil designs by jacobs (from naca) and the swept-wing concept by busemann.

so, transonic flight problems were well known...
imo, stack's merits are, that he was able to find the flaw in the design of the p-38, which was wrongly assumed to be more like flutter-caused, and not a consecutive effect, i think. high-speed research in the transonic area was done since long... kotcher was up to supersonic flight based on ackeret's theories, and after the war.

BigKahuna_GS
02-23-2009, 09:38 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">hi kahuna,

in addition, compressibility-effets were not only a problem in WWII fighters, but already discussed in the mid-20s and shown in 1934, when the (still) worldrecord-holder for sea-based planes found it's restriction at 709km/h due to compressibility </div></BLOCKQUOTE>


Rgr that Deepo-HP this is all very facinating reading.

At the NASA web site they have pictures dated back to German Proffeser Mach.

http://history.nasa.gov/SP-4219/4219-065.jpg
Photograph of a bullet in supersonic flight, published by Ernst Mach in 1887.


http://history.nasa.gov/SP-4219/4219-063.jpg
John Stack, Langley Research Center scientist, was Presented the Collier Trophy in 1947, awarded for his conception of transonic research airplanes. His research contributed to the X-1 breaking the sound barrier on October 14, 1947. (NASA Photo No. LMAL 48991).

http://history.nasa.gov/SP-4219/4219-064.jpg
Schematic of transonic flow over an airfoil. (a) Freestream flow slightIy below the speed of sound, typically a subsonic freestream Mach number from about 0.8 to 0.999. (b) Freestream flow Slightly above the speed of sound typically a supersonic freestream Mach number from 1.0 to about 1.2.

coyote40368
02-24-2009, 12:06 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VW-IceFire:
Yes...

Ju-87 Stuka (all but the anti-tank version)
Pe-2 (all versions)
SBD (both 3 and 5)
P-38L (not for dive bombing so much as high speed attack runs)
D3A Val
F4U Corsair (landing gear extends in an unlocked position for the purposes of dive bombing - a real feature!)

Probably left out some. </div></BLOCKQUOTE>

JU-88 A-4

deepo_HP
02-24-2009, 01:38 PM
hi kahuna,

the nasa-website is for sure one of the (if not the) most complete ressources in aerodynamics and surrounding sciences. i like it's very neutral and objective collection of research and the presentation for various levels of comprehension.
it could be slightly better organised in navigation and cross-linking... sometimes one can get easily lost.

however, rarely there is any organisation willing to make knowledge available in such a free manner and even offering educational tools in a great variety.