On this day in 1943 ......

[AndyG43]

.... the Dornier Do 335 'Pfeil' first took to the skies.

http://www.youtube.com/watch?v=jK8ydLY5QHQ

[AndyG43]

Oh yes, and on this day in 1940 North American flew the first example of the new British fighter, the NA-73X, soon to be called the Mustang. But I can't find a video of that flight, sorry.

[Skyhawk_310R]

The Pfiel was a great design in concept and was very fast. But, unfortunately it suffered terribly from overheating of the rear engine. Which is the same problem that the Cessna Skymaster also suffered from. However, I cannot agree with the caption the person made when he uploaded the video. The Do-335 was not faster than the P-51D. The Mustang was a 500 mph fighter and the Pfeil was not that fast.

But, then he made a greater and more questionable gaff when he asserted that the Fw-190 was superior to the P-51D. Nope, sorry, not even close.

Ken

[Allen]

The P-51D max speed was 442 mph at 26,000 feet using War Emergency power. The Racing P-51s after they are striped down and suped up are 500 MPH aircraft but the fastest fighting P-51 was the P-51H with a top speed of 487 mph but it was to late for Europe and the few in Pacific never made operational status.

Sorry the Dornier Do 335 'Pfeil' was faster than any P-51 in Europe.

[robert41]

From what I have read, the 335 was very fast. It had a number of problems besides overheating. Landing gear, hydraulic systems, poor pilot visibility.
The 335 was essentially an intruder aircraft, similar to the Mossie.
There were many versions. Bomber, heavy fighter, night fighter, recon, ect.
As a heavy fighter, it could have been faster than Allied fighters, but not as nimble. But with good tactics, and in good numbers with good pilots, the 335 might have made a dent in the Allied bombing campaign.
My opinion, a big waste of resources that could have been used elsewhere.

[Allen]

On the list of waste of resources the Do 335 is quite low...

[Skyhawk_310R]

From what I have read, the 335 was very fast. It had a number of problems besides overheating. Landing gear, hydraulic systems, poor pilot visibility.
The 335 was essentially an intruder aircraft, similar to the Mossie.
There were many versions. Bomber, heavy fighter, night fighter, recon, ect.
As a heavy fighter, it could have been faster than Allied fighters, but not as nimble. But with good tactics, and in good numbers with good pilots, the 335 might have made a dent in the Allied bombing campaign.
My opinion, a big waste of resources that could have been used elsewhere.

If you had your choice of Do-335 or Me-262, which one would you want? The single biggest mistake the Germans made in the air was not pouring all they had into the Me-262 and their engines. They had the right aircraft with the right engine design at the exact right time. Then, they chose to delay development and divert resources elsewhere.

Poor quality control in those jet engines was the biggest handicap the Me-262 had. But, if the Germans had devoted themselves to improving quality standards for those jet engines, stopped producing other fighters, then with a fleet of Me-262's with reliable engines, there would have been much more than a dent put into the Allied bombing effort over the ETO.

How good was the Me-262? The USAF in post war tests concluded that the Me-262 was better in all regards than the P-80 Shooting Star! That was a jet that went to war in Korea nearly ten years later! It should be noted that the Me-262 might well have held its own against the MiG-15 and F-86, again if the engines on the Me-262 had been manufactured to the standards required.

Back to my original question. The expert fighter pilots of the Luftwaffe wanted the Me-262, and as many as they could get. They knew due to bad engine builds, they had to baby the throttles. But, they also knew what they had their hands on. You are entirely correct that the Do-335 was a bad diversion of resources, but there were other diversions of resources far worse. It isn't often that a nation in dire situations has the means to defend themselves and turn their eyes to shinier toys. It would have been a very bitter blow to the British and Americans to see waves of Me-262's with good engines forcing them both to deploy their best jets and seeing them getting mauled by the Me-262's! There were a whole lot of British and American airmen who were most happy that the Germans squandered their opportunity.

Ken

[Skyhawk_310R]

Allen,

If we are going to compare, it makes sense to compare apples to apples and oranges to oranges. What is not fair is to compare one set of numbers to another set from two different situations. That said, the Do-335 was produced along the same timeline of that P-51H. Neither saw true combat. Twenty Do-335's were delivered to one unit that was slated for combat, but due to a variety of causes never really did. Fuel shortages, especially of the highly refined aviation fuel variety, were terribly acute by January 1945. That said, most sources say that the Do-335 was capable of sustained speed of 413 mph and a max of 477 mph. Bill Guston's "Combat Aircraft of World War II" documents this.

But, that does not account for the known engine overheat issues I previously spoke of. But, another problem was aerodynamic. Once the Pfiel got above 420 mph it started to porpoise and snake. This was acute enough where pilots slowed down from fear of developing into a catastrophic failure.

Pilots who flew the P-51D claimed they got more speed than the official numbers, and that was not uncommon for the official numbers to be below what the plane could achieve. Most of the official sources say the P-51D did 437 mph in the 25,500 to 26,000 foot area. So, why did the pilots claim much more? It came down to how much abuse of the engines were tolerated and what the airframe could safely sustain. But, from an aerodynamic standpoint, the Mustang could sustain that 437 mph and even higher. The Do-335 was relegated to the 413 mph mark due to chronic engine overheating and very bad aerodynamics above that speed.

Another case of under reporting performance was the Me-262. Official numbers report 550 mph or so. But, pilot reports claim much higher. Again, it was really a matter of how much abuse one was willing to put on the engines. Let's just say there are unsubstantiated pilot reports that claim Me-262's in shallow dives hit trans-sonic numbers, well above 600 mph and likely getting into the 650 mph range! Nevertheless, Bill Guston's book reports the speed of the Me-262 as 540 mph and pilots who flew it reported much more. It comes down to what the airframe could sustain and again the Do-335 had a terrible aerodynamic effect above 420 mph. So, even in a dive, it was speed limited. Yes, if you were willing to risk inflight destruction, you could get faster.

Could the aerodynamics of the Pfiel been fixed to allow it to get what it was capable of doing? Perhaps, but one will never know. On the other hand, the official speeds of the P-51H show what the airframe was capable of doing and often did do even in the earlier P-51D. That still doesn't account for the engine overheat. I doubt that could have ever been fixed. The Me-262 was capable of a lot more than it was limited to in the war. And it was not the design of it's engines that was the problem. The design was the basis for all future jet engines. It was a problem with poor manufacturing. That is shocking given the amazing quality control standards of German piston engines, which were amazing works of art produced in mass numbers.

Returning to the Mustang. The pilots had to do something to stay close enough to those Me-262's to shoot them down. Dives were common and more common were ambushes on Me-262's trying to land or takeoff. But, more than a few were shot down as the Me-262's were attacking bombers at full power. I strongly suspect, but cannot prove, that Dornier was feeling the heat of a totalitarian government and published the highest speed the aircraft could achieve even if it meant the plane was aerodynamically unstable to the point of nearly coming apart and the engines were destroyed upon landing! North American never felt that kind of heat. They did not have a reason to torture test their aircraft.

For all this, I maintain the Do-335 was not faster than a P-51D. You could get a P-51D to 500 mph and if you tried to do that with a Do-335, then based on many reports, it would likely have been a terminal maneuver.

Ken

[Blackbird686]

I watched a program on TV once about the Gloster Meteor and the Messerschmitt Me-262. The two had been restored to full operational status but the Meteor still had it's original jet engines whereas the Me-262 had been re-fitted with a set of Pratt and Whitney engines. With the newer engines, the capabilities of the 262's airframe literally came to life. As stated above, the engines used during WWII on the Me-262 were not up to par.... which, if you consider, Germany's remaining resources at the end of the war. Hitler basically rushed the Me-262 into production, without consideration to any additional testing or development. The facilities and assets available to the Germans were nothing short of minimal when the first Me-262 took to the skies... whereas England, somehow found the necessary time and resources to get the job done. As for the Do-335, here again....resources were scarce and time was running out for Germany. Had the time been allowed and the resources still available, the tide of the air campaigns may have tilted more in the Germans favor with the Me-262.

The P-51 Mustang was a stout aircraft however, and our pilots were more experienced, as they seemed to be able to "dodge the bullet" in aerial combat reasonably well. So they lived to fight another day. Germany and the Axis had experienced flyers, but they were few and far between towards the end of the war. Experienced airmen in those Mustangs and Spitfires eventually proved to be more than the Axis could handle.

BB686:USA-flag:

[robert41]

The single biggest mistake the Germans made in the air was not pouring all they had into the Me-262 and their engines

I agree with this. But early on, there was little need for such an aircraft. And nobody could foresee the massive Allied air power that was to come.

[Skyhawk_310R]

BTW: There was a post-war test done by the USAF of the Me-262. The test pilot's report indicated that in a shallow dive, his Me-262 experienced trans-sonic buffet in only a 20 degree dive, which is not much. He reported that this was "well above 600 mph," but at the altitude he was flying it was likely closer to 650 mph.

I saw that TV program on the Me-262 with the more modern engines. It was indicative of the "what could have been."

I'll just conclude by saying that if Luftwaffe test pilots were able to sustain 477 mph in a Do-335 for even 15 minutes, then a lot more than 20 would have been fielded. In terms of what a plane could sustain, I would actually rate the Dora-9 Fw-190 variant as faster. Speed isn't merely a reflection of how fast can you go just before the engines or airplane is destroyed! It really comes down to how fast can a pilot actually fly the aircraft operationally. The Me-262's were not merely attacking at 550 mph, they were screaming down at closer to 600 mph! And therefore, for the P-51D's to have any chance of getting off a quality shot, they screamed down on them at 500 mph.

It is also interesting to note that myopia was not limited to the Germans. What Frank Whittle had to endure from his own government would curl most peoples' toes! Whittle had a jet engine working more reliably early enough to have allowed the RAF to field squadrons of jets in 1942! In fact, with total dedication of resources, he might have had an operational jet before the war even started! But, he was given a pittance of a test budget. So austere were his test conditions that he personally carried out many of the tests and one almost killed him! Imagine the effect that would have had.

Of course, the design superiority of the Jumo engine in the Me-262 was due to the axial flow design, which allowed more power to be developed simply by increasing the length of the engine to increase the number of compressor and combustion stages, and keeping the diameter constant. Whittle's design required a larger diameter to achieve increased thrust, which of course increased drag. I have read some sources saying that the Me-262 could not have been fielded faster despite the infamous Hitler order for hanging a bomb on the frame. They wrote that the metallurgy of the compressor blades simply needed the time to mature even to the inadequate levels it did. But, considering what excellence the Germans could achieve, I believe if they put their full efforts into it, they could have fielded Me-262 units by late 1943. And if that had happened folks, I think the allies would not have achieved air superiority over continental Europe and one wonders if the Normandy invasion would have even happened? Remember, the entire strategic bombing campaign was changed around this time frame to regard outright destruction of targets as secondary to destroying the Luftwaffe fighter arm and achieving air superiority as a prerequisite for the invasion.

Putting engines behind each other has been a fool's gold trap in aviation for a long time. But, the problems always outweighed the benefits. The benefits are clear and undeniable -- all thrust along the centerline axis and greatly reduced cross section for greatly reduced parasitic drag. It wasn't until jet engines were laid tightly together facing rearward that this sort of advantage could actually be achieved.

Ken

[Allen]

You can abuse the aircraft to get more speed but it dosn't change a thing. The Do 335 is still faster in leval flight. It all has to do with drag and horsepower.

The Do 335 has the same if not more horsepower in one engine than the P-51D alone but the drag of the Do 335 is more than the P-51D not twice as much. (Do 335 max single engine speed was clocked at around 350 MPH)

The only thing that could keep the Do 335 speed down below that of the P-51d was the balls of the Do 335 pilot to push the aircrft.

As for the P-51D max speed. I read about it is 469 MPH by pilots but the Do 335 is still faster in commonly agreed upon top of 484 MPH to 487 MPH and that isn't likely it real max speed because rear engine wouldn't be at full power do to the overheating. Running both engines at full would have pushed over 500MPH in leval flight.

P-51H never made it out of the US of A by the fall or Germany and yet a Do 335 was almost in combat but for the pilot throttled up and left the attacking Hawker Tempests sucking on his exhaust.

[robert41]

I remember reading something about a captured 335 being flown back to the French coast by an Allied pilot, for shipment to Britain or the US. It had 2 P51 escorts, and outran them by a substantial amount of time. I believe it was something like 45 minutes, waiting for the 51's to catch up.
But I still say this aircraft was too late and unnecessary. By the middle of 44, Germany needed experienced pilots and fuel, not yet another new aircraft design.

[Skyhawk_310R]

You can abuse the aircraft to get more speed but it dosn't change a thing. The Do 335 is still faster in leval flight. It all has to do with drag and horsepower.

The Do 335 has the same if not more horsepower in one engine than the P-51D alone but the drag of the Do 335 is more than the P-51D not twice as much. (Do 335 max single engine speed was clocked at around 350 MPH)

The only thing that could keep the Do 335 speed down below that of the P-51d was the balls of the Do 335 pilot to push the aircrft.

As for the P-51D max speed. I read about it is 469 MPH by pilots but the Do 335 is still faster in commonly agreed upon top of 484 MPH to 487 MPH and that isn't likely it real max speed because rear engine wouldn't be at full power do to the overheating. Running both engines at full would have pushed over 500MPH in leval flight.

P-51H never made it out of the US of A by the fall or Germany and yet a Do 335 was almost in combat but for the pilot throttled up and left the attacking Hawker Tempests sucking on his exhaust.

Well, OK, but before I would say "... balls of the Do-335 pilot to push the aircraft," I would recommend you first get in an airplane that starts to porpoise and snake when passing 420 mph and see how you would react.

Cheers,

Ken

[Bjoern]

On this day I saw you
and you saw me
in a 'Pfeil'
in 1943



I need some sleep...

[hairyspin]

The Do-335 was relegated to the 413 mph mark due to chronic engine overheating and very bad aerodynamics above that speed .... and again the Do-335 had a terrible aerodynamic effect above 420 mph. So, even in a dive, it was speed limited.

:kilroy: Where is that documented? Just interested.

[Skyhawk_310R]

:kilroy: Where is that documented? Just interested.

Numerous historical sources, but the one on my shelf I immediately pulled down was Bill Guston's "Combat Aircraft of World War II." Years ago, when doing some side work for Tom Wood and his company SimTech, we had to research the issue to develop the flight model for their Do-335 Pfeil. Sadly, a review of online sources omit all reference to this issue, and one online website had the audacity to write that the aircraft was devoid of any design flaws!

Certainly such a statement flies in the reality of the engine overheating issue and the aerodynamic issues. Interestingly, there was another very serious issue that killed two of the test pilots who tried to test out the ejection seat system. Due to the rear propeller and vertical stabilizer height above the cockpit, a normal bailout was considered impossible. Yet, the ejection process involved the release of the rear propeller, which apparently went well, followed by the release of the stabilizers, which also seemed to go well, but then the pilot was to reach up on the canopy and pull a couple of quick release latches. Problem is that both test pilots who did this process were found ejected from the aircraft dead with broken arms. The first broke both arms and the second broke one. Since both were dead neither could report what happened. It was theorized that the canopy departed so fast and rapidly that the pilots were unable to release their grips on the latches and had their arms horribly dislocated and fractured! Then, without arms functional, they were ejected out by the seat!

Such situations show how totally dangerous it was to be a test pilot in this era!

Ken

[hairyspin]

Thank you. Eric Brown also describes the escape process in Wings On My Sleeve.

[AndyG43]

Thank you. Eric Brown also describes the escape process in Wings On My Sleeve.

AsI recall, Captain Brown was mildly impressed with the Pfeil, thought it had a lot of potential especially in the night fighter role; I suspect that the porpoising could have been ironed out given time, but time was not on their side.

[Skyhawk_310R]

AsI recall, Captain Brown was mildly impressed with the Pfeil, thought it had a lot of potential especially in the night fighter role; I suspect that the porpoising could have been ironed out given time, but time was not on their side.

I suspect that is true, but of course there is no way we can ever know. However, if putting propeller driven engines behind each other and achieving great success was achievable, it would have been almost exclusively done. Ultimately, the prop on the front disturbs airflow to such a degree that it is impossible to get a sufficient quantity of cold air into the rear engine in order to ensure it stays cool. This is also the case when designers tried to place the two engines immediately behind each other and rely upon the single air intake to cool both.

This is why the traditional lateral layout of multiple engines has stayed the trend. I feel secure in saying this because of all the myriad of problems present when you lay out piston prop engines in lateral layout, primarily the asymetrical thrust when one engine fails. It is a handful and in most cases robs the pilot of about 75% of thrust when just one of two engines are lost!

I'm very confident that the best environment for the Do-335 to operate in is low level where the excess horsepower can be more safely used and therefore would allow the aircraft to fly faster in level flight than other single engine fighters. But, at high altitude, or in cases where a fast single engine fighter could dive down, I don't think that excess power would have been as helpful without that aerodynamic issue being solved.

It was not until the propeller went goodbye that putting engines very tightly together became prudent. This is also why the FAA has a centerline thrust restriction on pilots who fly such jets -- because the aerodynamics of losing an engine is so much easier to handle.

One last point on this theme. If level speed was the ultimate measuring stick for a fighter, then the P-40 would have been hopeless against the A6M Zero. In reality, it was just the opposite. The Zero was undeniably faster in level flight than was the P-40. But, the P-40 was aerodynamically able to dive very fast and therefore that made the P-40 a lethal weapon against the Zero and able to hold its own until new fighters came that could even go faster than the Zero in level flight. BTW: The IJN recognized this reality because they modified the Zero with thicker and heavier leading edges on the wings that sacrificed weight and a small bit of level speed, but allowed the Zero to dive slightly faster. This was a painful recognition of the reality. Speed in aviation is three dimensional!

And in truth, speed being three dimensional, is also the heart of the weakness of the Mustang! The P-51's famous laminar flow wing reduced parasitic and induced drag in level and diving flight. But, it made for a very poor climber! The P-51 would have been a lousy interceptor. The Spitfire was ideal in the Battle of Britain because that beautiful elliptical wing made the Spit a magnificent climber with a very fast climb rate. The P-51 would have been several thousands of feet lower by the time the Spitfire climbed up to intercept the German bombers and fighters at altitude. Again, excess horsepower in the Pfeil would, in theory, had made it a great interceptor, but that rear engine overheat would have reared its ugly head most terribly when in a sustained climb due to the lack of cool airflow. In other words, everything in aviation has a price and that price is normally a tradeoff to achieve greatness in one area and experience degradation in others.

Ken