Why Did the He 177 Fail?

[SpicyJuan11]

Hello, I am quite confused as to why the He 177 failed. I originally thought that it was due to the "welded together engines", but reading through a couple threads, I actually heard that the coupled engines actually worked fine and quite reliably, but the issue was that Heinkel failed to produce a good engine cowling/nacelle(?)which led to improper cooling and engine fires, not to mention that the air-frame was burdened by the dive-bombing requirement. Is this true? Any help would be greatly appreciated.

 

[tyrodtom]

Just think you've got 2 inverted V-12s side by side, the center 6 exhaust manifolds of each engine are either shared or very close together, in the bottom of the engine nacelle .

No engine is perfect. Some of them have tiny leaks, any leaked oil or any oil residue left from hurried routine maintenance, is going to end up at the bottom of the engine nacelle, which happens to be where the hottest area is.
If you look at a cutaway of the He177, see if you can see a firewall between the engine and the main spar of the wing. If there is no firewall, a engine fire won't take long to cause main spar failure. Also the engine oil tank is right behind that main spar, but they usually are close to the engine.

I'd say poor design decisions on both engine builder and airframe builder part.

 

[SpicyJuan11]

Just think you've got 2 inverted V-12s side by side, the center 6 exhaust manifolds of each engine are either shared or very close together, in the bottom of the engine nacelle .

No engine is perfect. Some of them have tiny leaks, any leaked oil or any oil residue left from hurried routine maintenance, is going to end up at the bottom of the engine nacelle, which happens to be where the hottest area is.
If you look at a cutaway of the He177, see if you can see a firewall between the engine and the main spar of the wing. If there is no firewall, a engine fire won't take long to cause main spar failure. Also the engine oil tank is right behind that main spar, but they usually are close to the engine.

I'd say poor design decisions on both engine builder and airframe builder part.

So what would it take to make it successful (the engine in the airframe and the aircraft itself)?

 

[pbehn]

Impolite to answer a question with a question but where could it have been successful?

 

[SpicyJuan11]

Impolite to answer a question with a question but where could it have been successful?

The question is not if it could have been operationally successful, rather technically successful. Also, it's best to ask this question in another thread, I'd rather not have this thread get off topic.

 

[Greyman]

During interrogation of Dr. Ernst Heinkel at the end of WWII, I suggested to him that his organisation seemed to enjoy more success with smaller aeroplanes than with large ones. His face displayed some annoyance when he replied that I must be referring to 'that accursed 177'. He associated Ernst Udet, the former Generalluftzeugmeister, in his mind with the whole disastrous story, and in particular the demand for a 60-degree diving attack capability which he blamed on Udet's influence.

Heinkel himself had not been very closely involved with the original design of the He 177. Dipl-Ing Heinrich Hertel had been Heinkel's Technical Director and Chief of Development during the initial development of the bomber but had left the Heinkel organisation in March 1939, and his departure at this juncture had not augured well for the future of the aircraft. In fact, in 1942, Hertel had returned to Heinkel as Reichsluftfahrtministerium Deputy with full powers to reorganise the development of the He 177. But it proved to be a case of closing the stable door after the horse had bolted, and Ernst Heinkel summed up his feelings when he said to me: 'I even look more kindly on the He 111Z than that 177!'

- Eric Brown

So what would it take to make it successful (the engine in the airframe and the aircraft itself)?

I think, as Heinkel said, the basic design was cursed and a return to the drawing board would be needed.

 

[tomo pauk]

Methinks that choice of powerplant was the main problem. The dive bombing request and its implementation was not easing the situation either.

 

[Denniss]

The dive bombing requirement forced Heinkel to strengthen the airframe to withstand the stress of dive bombing. This caused extra weight and required the use of two engines as the wing was not able to cope with stress caused by an outer wing engine in a 4-engine setup. Due to insufficient power from a single engine they used the coupled engines. The coupled engine was tightly integrated into the wing and that is one major cause of the issue with engine fires (too tight, improperly shielded), I can only assume this was initially made to reduce/limit CoG shifts (which would have forced even more weight in the rear to counter this).
The DB 605 as base engine of the later DB 610 couple added its own share of problems but those should have been solved/reduced by late 1943.

The aerodynamically good/clean design (also caused by twin engien setup) had positive aspects - the aircraft had rather high speeds which could be improved by using a shallow glide approach to target and away from it. During operations over England in 43/44 the He 177 had the lowest loss rate of the involved bombers, most likely due to their speed advantage.

 

[GregP]

I have jeard other people call it a shallow glide approach but it wasn't at all.

It was a shallow dive approach with power on. A glide is either engine off or power at idle.

The B-29's also used this approach in Japan when bombing accuracy from 30,000 feet wasn't all that was desired. It gave them an over-the-target speed of 330 mph or so, making them very difficult to catch and even they did get caught, the attacker had one pass at best and then was fuel limited for a second pass in large part.

 

[SpicyJuan11]

I think, as Heinkel said, the basic design was cursed and a return to the drawing board would be needed.

So what changes had to be made on the drawing board? Or would there have been so many changes that it would've been an entirely new aircraft?

Methinks that choice of powerplant was the main problem. The dive bombing request and its implementation was not easing the situation either.

But didn't it work reliably in tests?

The dive bombing requirement forced Heinkel to strengthen the airframe to withstand the stress of dive bombing. This caused extra weight and required the use of two engines as the wing was not able to cope with stress caused by an outer wing engine in a 4-engine setup. Due to insufficient power from a single engine they used the coupled engines. The coupled engine was tightly integrated into the wing and that is one major cause of the issue with engine fires (too tight, improperly shielded), I can only assume this was initially made to reduce/limit CoG shifts (which would have forced even more weight in the rear to counter this).
The DB 605 as base engine of the later DB 610 couple added its own share of problems but those should have been solved/reduced by late 1943.

The aerodynamically good/clean design (also caused by twin engine setup) had positive aspects - the aircraft had rather high speeds which could be improved by using a shallow glide approach to target and away from it. During operations over England in 43/44 the He 177 had the lowest loss rate of the involved bombers, most likely due to their speed advantage.

So could the engine cooling, etc, have been resolved by a redesigned nacelle? How about a pusher/puller such as on the Do 335 and Do 215/216?

 

[Shortround6]

If you are going to use push-pull you better decide at the start. Shifting a pair of engines from the front of the wing to the back plays havoc with the CG.
It also pretty much dictates tricycle landing gear as a tail dragger with props on the back of the wing either needs stilts for landing gear or very small props.

 

[SpicyJuan11]

If you are going to use push-pull you better decide at the start. Shifting a pair of engines from the front of the wing to the back plays havoc with the CG.
It also pretty much dictates tricycle landing gear as a tail dragger with props on the back of the wing either needs stilts for landing gear or very small props.

Well obviously the wings will need some redesign like the He 177B, but it shouldn't be too much of an issue, right?

 

[kool kitty89]

Just think you've got 2 inverted V-12s side by side, the center 6 exhaust manifolds of each engine are either shared or very close together, in the bottom of the engine nacelle .

No engine is perfect. Some of them have tiny leaks, any leaked oil or any oil residue left from hurried routine maintenance, is going to end up at the bottom of the engine nacelle, which happens to be where the hottest area is.
If you look at a cutaway of the He177, see if you can see a firewall between the engine and the main spar of the wing. If there is no firewall, a engine fire won't take long to cause main spar failure. Also the engine oil tank is right behind that main spar, but they usually are close to the engine.

Wouldn't a lot of those problems have been avoided if upright V orientation had been adopted rather than the inverted V?

 

[Koopernic]

Well obviously the wings will need some redesign like the He 177B, but it shouldn't be too much of an issue, right?

Quite a few successful Dornier sea planes flew with the push-pull arrangement. One of them the Do 26 was one of the longest ranged aircraft ever built.

The He 177's problems stem from a number of situation unique to the German predicament
1 The lack of resources to develop competitive alternatives and flyoffs. EG the UK had Lancaster, Stirling Halifax, the US B-17 and B-24.
2 The need for tactical aircraft to deal with difficult neighbours already on the border.
3 Certain psychological factors associated with risk management of complex projects.
4 Funds sunk into the highly ambitious Bomber B project which had effectively heavy bomber range and bombload which failed to mature due to overly ambitious engine requirements.

 

[johnbr]

Me I think the redesign was the he-274.

 

[davebender]

Primary reason for failure of engine cowlings on early model He-177A was due to a poorly designed oil tank. Vibration caused fatigue cracks which allowed oil to drip onto hot engine and exhaust system components. After that engine fire is only a matter of time. The problem was fixed after 145 production aircraft.

For comparison purposes...
Avro built 202 Manchester bombers before technical problems were fixed resulting in the Lancaster bomber.

Boeing built 120 early model B-17s before the extensively modified B-17E entered production.

If we are comparing to contemporary heavy bombers the He-177A teething problems were not particularly bad. Difference is He-177 program received crumbs for funding compared to Lancaster and B-17. So Heinkel did not receive funding to build 7,000+ perfected He-177A heavy bombers after teething problems were fixed as Avro Lancaster and Boeing B-17 did.

 

[Shortround6]

Quite a few successful Dornier sea planes flew with the push-pull arrangement. One of them the Do 26 was one of the longest ranged aircraft ever built.

They only built six Do 26 aircraft. A little hard to tell how successful it might have been. A couple of reasons for the Push pull on the Do 18 was ease of maintenance, engines are over the hull and wing giving mechanics a place to stand.

another was the fact that such an arrangement helped keep the prop/s out of the spray.
Did the Do 26 achieve such range because of the push pull arrangement or is spite of it?

 

[pbehn]

During operations over England in 43/44 the He 177 had the lowest loss rate of the involved bombers, most likely due to their speed advantage.

Did they hit anything of note? Night bombing needed a huge investment not only in aircraft but in training and technology. The He177 may have had the lowest losses but they were unsustainable for the LW and also the same loss rate would have been borderline long term for the RAF/USAF. If they continued the losses would have increased when the surprise factor was lost.

 

[Greyman]

Were there any German pilots that spoke of it in a positive light? The only real commentary I have read is from Eric Brown - and he was not fond of it ... to put it mildly.

 

[SpicyJuan11]

Were there any German pilots that spoke of it in a positive light? The only real commentary I have read is from Eric Brown - and he was not fond of it ... to put it mildly.

Werner Lerche thought that the He 177 airframe was great.