Alternate Approach to the P-38 Compressibility Problem (1 Viewer)

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MIflyer

Captain
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May 30, 2011
Cape Canaveral
I have seen some very questionable videos about WW2 aircraft on Youtube but I watched one tonight that seems to have some new information.

We have all heard about the P-38's compressibility problem and how the "dive flaps" ultimately solved it, but according to the video a different approach was developed in the fall of 1943. A P-38 pilot dove after a German fighter and got into compressibility. Luftwaffe pilots had learned to dive quickly away when bounced by P-38's at altitudes of 18,000 ft and above but to use a shallow angle to trick the P-38's int entering the compressibility regime. Desperate to do something to regain control of the airplane, the P-38 pilot tried shutting down his Right engine. To his amazement he found that he regained control and that he could actually speed up, to over 500 mph, and catch the German fighter he was diving after, and shot it down. Then he restarted the engine at 12,000 ft and went home.

Back home he reported on this approach and was told he was nuts. Then they found out it worked. Over the objections of the maintenance personnel, who were appalled by shutting down an engine in dive and then restarting it, a procedure for the technique was developed and published in March 1944. The Germans eventually found out about it from a captured P-38 pilot and revised their tactics accordingly. It was still used in the ETO until the end of the war.

Never heard about this before!
 
Can you give a source for this?
Go do a search on Youtube is the best thing I can tell you.

Within the video they cited specific units, dates and pilot names as well as the release of directives by 8th AF, but where else you'd find them I do not know. I am surprised that Warren Bodie's monumental work on the P-38 did not mention this, that I can recall.

On the other hand I saw a video a little while back on Youtube about the P-38 that I am at least 90% sure is fabricated bunk, but I have not yet done the research to find out definitely.
 
MIflyer

Is this the video you are referring to?

Pilot Workarounds: Some pilots resorted to shutting down one engine mid-dive to reduce speed and regain control—a desperate but occasionally effective tactic.

Search:

WW2 secrets P-38 dive problem

Hopefully you will get the video.
Eagledad
 
Logically, I do not see how shutting down one engine would solve the problem. The P-47 had the same problem with compressibility. It is with air flow starting to go supersonic over the wings. Then again, I am no expert and could be wrong.
Question for the experts here. Did either the Me-109s or the Fw-190s have similar problems with compressibility?
 
Question for the experts here. Did either the Me-109s or the Fw-190s have similar problems with compressibility?
The BF-109 and FW-190 had heavy elevators, especially at high speed, so much so that it imposed limitations from pulling out of dives. So maybe they were disinclined to go fast enough to encounter compressibility.
 
The BF-109 and FW-190 had heavy elevators, especially at high speed, so much so that it imposed limitations from pulling out of dives. So maybe they were disinclined to go fast enough to encounter compressibility.
"Dive[
The Fw 190 has a high rate of dive, the initial acceleration being excellent. The maximum speed so far obtained in a dive is 580 m.p.h. |934 k.m./h.l True at 16,000 ft [4,880 m|, and at this speed the controls, although slightly heavier, are still remarkably light. One very g<x>d feature is that no alteration of trim form level flight is required either during the entry or during the pull-out. Due to the fuel injection system it is possible to enter the dive by pushing the control column forward without the engine cutting."

 
The BF-109 and FW-190 had heavy elevators, especially at high speed, so much so that it imposed limitations from pulling out of dives. So maybe they were disinclined to go fast enough to encounter compressibility.
Hi Miflyer,
What you're saying contradicts the FW factory dive report (available here ).
If you look at the graphs, when starting the recovery from M0.76 , the force applied to the stick is max 27/28Kg at 5800m. This is actually very light for a recovery from such speeds.

Note the Würger , even in the recovery phase, was still accelerating , inertia momentum?
190dive.jpg
 
That is not what Capt Eric 'Winkle" Brown said in his writings.
Googles AI says "Based on his flight testing, Captain Eric "Winkle" Brown noted that the Focke-Wulf Fw 190 had very responsive and easy controls during a high-speed dive, unlike other fighters of the time. "
 
Gentlemen,

In Capt. Eric Brown's book, "Wings of the Luftwaffe" page 84, referring to the FW-190A-4/U8 (which had its external racks removed), he wrote "the elevators proved to be heavy at all speeds and particularly so above 350 mph (563 km h) when they became heavy enough to impose a tactical restriction on the fighter as regards pull-out from low-level dives."

Brown repeated those words about the FW-190A-4 in his book, "Duels in the Sky".

As for the BF-109G, Brown wrote "although the Bf-109G pilots tended to use a bunt into a steep dive as an escape manoeuvre in dogfights, they had some very heavy rudder and elevator control forces to contend with as speed built up and pull-outs at low altitude had to be made with considerable circumspection." (quote from "Wings of the Luftwaffe" page 151).

FWIW

Eagledad
 
Yep, Eagledad, same source. I did not look in Duels in the Sky, but I will look in the book on testing of fighters at Boscome Down when I figure out wherethell I put it.
 
On one side, we have manufacturer numbers, on other side we have "feelings" or personal opinions. i know which one i choose.
Do we know what position was the vertical tail on when Brown did the dive? if trimmed for level flight, wel then this could explain a lot... but we do not know it cause he didn't wrote it.
Brown could have made mistakes (and not only with the FW) just because he tried the planes, and didn't flew them daily so he hadn't the right reflexes to adjust what was supposed to be adjusted?
Which would would you put faith in:
a factory test pilot doing a programmed test with specific instruments dedicated to the test build in the airplane or the casual test pilot that fly a plane for an hour max?
 
Googles AI says "Based on his flight testing, Captain Eric "Winkle" Brown noted that the Focke-Wulf Fw 190 had very responsive and easy controls during a high-speed dive, unlike other fighters of the time. "
Google's AI says some pretty weird things. I wonder if they'll ever actually get the bugs ironed out?
 
Capt Brown had a LOT of experience with the FW-190. His father was a WW1 pilot who got to know a number of the German pilots. Before the war "Winkle" was teaching English in Germany and when the war was about to started they came and got him, locked him up and then a few days later led him and his car to the Swiss border and told him to leave.
In addition to evaluating captured examples during and after the war he led a team looking around abandoned Luftwaffe airfields for suitable acquisitions even before the war was over. On one in Holland, I think, he found a perfectly serviceable FW-190, cranked it up, and flew off to check on other airfields in the area. Now, would flying around in an enemy aircraft while the shooting was still going on be a good idea? I think not, but he got away with it.
 
Gentlemen

The Focke Wulf report is for a dive starting at 10000 meters and ending at 5000 meters. Brown's quotes are for dives completed at low level, kind of an apples to oranges comparison. The response that I wrote was to the AI quote "Based on his flight testing, Captain Eric "Winkle" Brown noted that the Focke-Wulf Fw 190 had very responsive and easy controls during a high-speed dive, unlike other fighters of the time. ". It would appear that AI missed on that one.

In re-reading the FW test report, please note the test pilot's impressions, and that there was a time during the dive that the pilot felt that the elevator was ineffective.

FWIW

Eagledad
 
It is certainly possible that Brown made a mistake. He also had more different aircraft in his logbook than another pilot in any airforce. Perhaps someone has beaten this record since then. Some aircraft he flew with only a short cockpit check with a German mechanic helping him.
I will also note that one Bell pilot got an early P-39 up to 394mph. No other pilot in any other P-39 got within 15mph for several years.
Of course no other pilot was running hundreds of pounds light, had 20 coats of paint, sanded between most coats and several pounds of filler fairing in the windscreen/canopy. That 394mph figure was just within tolerance of the 400mph guarantee speed to satisfy the contract requirement.
Point is that some factory figures may not be identical to real world performance.
Brown also landed and flew a P-39 off a small British carrier, although the plane was well under normal gross weight.

He had done around 15 simulated landings during an assessment study of using a plane with no landing gear and a flexible fight deck.
 
I would take anything you see and hear on Youtube with a grain of salt. There is one channel on Youtube that covers World War 2 history and every story they post you know in the first few minutes that its made up.
 

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