Heinkel He 177A-7 high-altitude bomber

[Vahe Demirjian]

I found pictures of the Heinkel He 177A-7 at these links:

Harold A. Skaarup Web page
File:Bundesarchiv Bild 146-1972-065-68, Flugzeug Heinkel He 177 A-7.jpg - Wikimedia Commons

The He 177A-7, if anyone is aware, was a high-altitude He 177 variant with a wingspan of 118 feet and the rear manned dorsal gun turret dispensed with. Six He 177A-5s (one of which, GP+RY/ Wk-Nr 550256, is featured in the photos in the above-mentioned links) were modified to He 177A-7 configuration to test the wing of the He 177A-7. The He 177A-7 also formed the basis of the He 177B-7 (originally He 177A-10), which had the same wingspan and lack of rear dorsal gun turret but utilized four separate engines.

 

[Propellorhead]

Standard He177 bomb payload trade off with fuel carried:

The RLM convened a meeting of manufacturers Heinkel, Junkers & Messerschmitt 11 January 1944 at Vienna to discuss the future of the severely underpowered Me264. From this emerged a proposal to use wings from the Me264 to create a hybrid He177 powered by the DB613 Doppelmoteren, which combined two DB603 engines on a common gearbox & propeller shaft akin to the earlier DB606 , OR DB610.

The RLM planning group predicted a 56,000kg aircraft able to fly12,500km

[Source: Page 96-98 from the book "Heinkel He.177, 277, 274" by Manfred Griehl and Joachim Dressel (Airlife Publishing Ltd.)]
Having spoken to the researcher for Manfred Griehl, I know the information was unearthed from Heinkel company archives.

The resulting 3,800hp DB613 had a displacement of 60 Litres versus 55L on the B29's 3,70hp Wright R-3350. Ironically had the original Me264 been repowered with four DB613 engines it might have performed better than the B29.

DB613 Engine source , Daimler Benz Werk 60, Kntruktionsbericht.K21
from 21.01.1944 ( Daimler Benz factory 60, construction report K21 date 21 January 1944)

In a standard He177 the total fuel capacity was 10,400 Litres (7,498kg) with 1,761 Litres in each wing. optionally 1520 Litres in the forward bomb bay. Adding wings from the Me264, provided 9,740kg per wing. ie 10,400L + (13,509Lx 2)=37,418 Litres -Total

Naturally with so much extra weight this hybrid He177 needed much more power to get airborne.
According to former Luftwaffe pilot Peter Brill, speaking in 2005, the DB613 engines drove contra rotating propellers and once in flight, an engine in each pair could be declutched and shut down to extend range.

Because the DB613 comprises a pair of DB603 engines and the '603 could be boosted with Methanol , I would not be surprised if they boosted power briefly to 4,000hp for take off. Obviously that could only happen for a matter of minutes or it would cause overheating, but take off is when power is most needed.

Peter Brill referred to the hybrid aircraft as the AK177, others have referred to it as the Ju177. It is also referred to as the He177 A-7R2

the hybrid had

Crew: 5
Powerplant: 2x*DB 613
Output(each): 3,800hp
Wing Span: 31.50m (103 ft 8in)
Weight (loaded): 34.700 kg (76.500 lb)
Max Speed*: 425 km/h (264 mph)
Ceiling: 8.000m (26,247 ft)
Range: 4.600 km (2.858 miles)
Armament
Nose (lower): 1*FDL 131Z
Dorsal(fwd): 1* FDL 151Z
Dorsal(aft): -
Ventral: 1* WL 131Z
Tail: 1*HL 131V

Keep in mind , only four hybrid 177 ever flew according to Peter Brill at the Sabadell seminar in 2005.
It would have been a true strategic bomber.

(below) Me264 wing

 

[SaparotRob]

How come when all systems are knocked out, including life support, artificial gravity always works?

 

[wuzak]

The resulting 3,800hp DB613 had a displacement of 60 Litres versus 55L on the B29's 3,70hp Wright R-3350. Ironically had the original Me264 been repowered with four DB613 engines it might have performed better than the B29.

The DB 603 had a capacity of 44.5L, so the DB 613 would have a capacity of 89.0L.

For reference:
DB 606 = 2 x DB 601 = 2 x 33.9L = 67.8L
DB 610 = 2 x DB 605 = 2 x 35.7L = 71.4L

Given that you, or your source, claims 2 x 44.5L = 60L I wonder about the veracity of the rest of the post.

The weight of these coupled power plants was more than double the weight of a single engine, as each half was a complete base engine, save for the reduction gear, and there was a new gearbox with clutches to combine their power.

The DB 613 would weigh > 1,800kg/4,000lb.

Some versions of the DB 603 could, indeed, produce 2,000hp for take-off. Even at that, the DB 613 would be no better than 1hp per lb.

The Wright R-3350 never produced 3,700hp in a B-29. 3,700hp was for the post war turbo-compound versions found in commercial aircraft. By that time the B-29 had gone to the R-4360 and become the B-50.

The most power wartime B-29s had was ~2,700hp from each of its R-3350s. Most had only 2,200hp. However, these were turbocharged, so could maintain their power at that level to a high altitude (> 25,000ft, IIRC), whereas no service DB 603 was ever used with a turbo.

Naturally with so much extra weight this hybrid He177 needed much more power to get airborne.
According to former Luftwaffe pilot Peter Brill, speaking in 2005, the DB613 engines drove contra rotating propellers and once in flight, an engine in each pair could be declutched and shut down to extend range.

The coupled engines DB 606, DB 610 and DB 613 drove a single propeller through a gearbox that connected the two engines. Each of the engines could be isolated from the other by use of a clutch.

A DB 613 with dual rotation propeller would have been easier to make and get working. But I am uncertain as to whether that was done.

 

[wuzak]

Come to think of it, the DB 609 was around 60L - 61.6L in fact - with a bore and stroke of 165 x 180mm and 16 cylinders. It was not a coupled or doubled engine, but a single inverted V-16, a development of the DB 603.

Max power was ~2,700hp.

It could be configured with different types of reduction gear, including a contra-prop. But it was cancelled in order to concentrate on engines that were already in production.

 

[nuuumannn]

It would have been a true strategic bomber.

would'a could'a should'a... If only they could get over the chronic unreliability and maintenance issues the aircraft suffered from, it would'a been awesome, but it wasn't.

 

[nuuumannn]

Peter Brill referred to the hybrid aircraft as the AK177, others have referred to it as the Ju177. It is also referred to as the He177 A-7R2

Hey Propellorhead, you've spelt "propeller" wrong in your online moniker, did you know that? Two 'E's, one 'O'.

So here's something for you to consider the next time you pop by to take a look at what's being said in response to what you are posting. On this site we pride ourselves on the accuracy of our knowledge and the veracity of our stance. We collectively have experience from many different disciplines and industries, but all have a love of aviation based on credible facts. We dabble in what-ifs, but are clear in stipulating that that is indeed what they are.

This means that your recent posts exclaiming that the Germans detonated a nuclear bomb in 1945 and your support for the whole Ju 390 bombing New York story instantly puts you in a position where anything you post will be regarded with scepticism.

This steadfast adherence to fantastic propositions places you in the rabid conspiracy theory-promoting group of aircraft enthusiasts, of which, as you are probably aware there is little tolerance for here. So, might I suggest another place where you can post whatever you like that won't instantly be disregarded the moment you post it? Because, from what I've read of what you have recently posted, this isn't really the place for you.

Not saying you should leave or anything, that's not up to me, but it might be worth considering given the nature of your presence here.

 

[nuuumannn]

Joe, just sent you a PM.

 

[Thos9]

The most power wartime B-29s had was ~2,700hp from each of its R-3350s

Can you provide a source please?

 

[wuzak]

Can you provide a source please?

No, I'm sure I read it somewhere but can't recall where.

Most sources quote the R-3350 used in the B-29 as having maximum power of 2,200hp.

Wiki has some numbers:

Wright R-3350 Duplex-Cyclone - Wikipedia

en.wikipedia.org

B-29 quoted as 2,200hp

Boeing B-29 Superfortress - Wikipedia

en.wikipedia.org

Lockheed Constellation C121A with 2,500hp

Lockheed C-121 Constellation - Wikipedia

en.wikipedia.org

Skyraider 2,700hp

Douglas A-1 Skyraider - Wikipedia

en.wikipedia.org

 

[FLYBOYJ]

I believe the engines installed on the Silverplate B-29s were pushing about 2,700 HP

 

[Thos9]

I believe the engines installed on the Silverplate B-29s were pushing about 2,700 HP

Can you provide a source please?

 

[FLYBOYJ]

Can you provide a source please?

There are plenty of on line sources that you can easily access...

Silverplate - Wikipedia

en.wikipedia.org

Wright R-3350-23 Duplex-Cyclone

The Wright R-3350 Duplex-Cyclone was one of the most powerful radial aircraft engines produced by the United States. Based on the earlier Wright Cyclone engines, the R-3350 first ran in May 1937, and

www.nationalmuseum.af.mil

And I'll stand corrected, the R3350-41 was shown to put out 2200 HP (I was probably remembering the RPM numbers) but were fuel injected and said to be more reliable then the -23 engines. You could research the reference for that.

Like its sistership, Enola Gay, 44-27297 was a specially modified "Silverplate" B-29. The Silverplate B-29s differed from the standard production bombers in many ways. They were approximately 6,000 pounds (2,722 kilograms) lighter. The bomber carried no armor. Additional fuel tanks were installed in the rear bomb bay. The bomb bay doors were operated by quick-acting pneumatic systems. The bomb release mechanism in the forward bomb bay was replaced by a single-point release as was used in special British Lancaster bombers. A weaponeer's control station was added to the cockpit to monitor the special bomb systems.

Bockscar had four air-cooled, supercharged, 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division R-3350-41 (Cyclone 18 787C18BA3) two-row 18-cylinder radial engines with direct fuel injection. The R-3350-41 had a compression ratio of 6.85:1 and required 100/130 aviation gasoline. It was rated at 2,000 horsepower at 2,400 r.p.m. at Sea Level, and 2,200 horsepower at 2,800 r.p.m, for take-off. The engines drove four-bladed Curtiss Electric reversible-pitch propellers with a diameter of 16 feet, 8 inches (5.080 meters), through a 0.35:1 gear reduction. The R-3350-41 was 6 feet, 2.26 inches (1.937 meters) long, 4 feet, 7.78 inches (1.417 meters) in diameter and weighed 2,725 pounds (1,236 kilograms).

Wright R-3350-41 | This Day in Aviation

 

[Snautzer01]

Reversible prop. Why? To help stop when pilot had to abort start? Important cargo

And why the souped up bomb bay doors? They flew with only a few planes to the target not to attrack attention of defence. So had time i think.

 

[FLYBOYJ]

Reversible prop. Why? To help stop when pilot had to abort start? Important cargo

Exactly

And why the souped up bomb bay doors? They flew with only a few planes to the target not to attrack attention of defence. So had time i think.

You are not going to be able to do any abrupt evasive maneuvers with the bomb bay doors open. Once you deliver the payload you want to get out of the area as quick as possible.

 

[Snautzer01]

You are not going to be able to do any abrupt evasive maneuvers with the bomb bay doors open. Once you deliver the payload you want to get out of the area as quick as possible.

Sure but cannot be that a big a diff in closing time. Big boom or not. And they where high up.

 

[FLYBOYJ]

Sure but cannot be that a big a diff in closing time. Big boom or not. And they where high up.

When you're delivering a nuclear weapon over enemy territory, I would say "seconds matter". The quicker you can clean up the aircraft (closing the bomb bay doors) the better.

 

[Snautzer01]

When you're delivering a nuclear weapon over enemy territory, I would say "seconds matter". The quicker you can clean up the aircraft (closing the bomb bay doors) the better.

Just info

B-29 Bomb-Bay & Silverplate

From what I remember being told, the initial nuclear-bomb design was to require a bomb-bay of 33-feet. This would have required the B-29's bomb-bay to be re-designed from two individual bays to one single huge bay. What structural modifications were needed to make this so?

ww2aircraft.net

and Winker or Winkler type bomb bay. I get the impression that with the normal ones it couldnt work over the distance the bomb bay now had

From In Detail & Scale B-29 Superfortress

 

[FLYBOYJ]

Just info

B-29 Bomb-Bay & Silverplate

From what I remember being told, the initial nuclear-bomb design was to require a bomb-bay of 33-feet. This would have required the B-29's bomb-bay to be re-designed from two individual bays to one single huge bay. What structural modifications were needed to make this so?

ww2aircraft.net

and Winker or Winkler type bomb bay. I get the impression that with the normal ones it couldnt work over the distance the bomb bay now had

From In Detail & Scale B-29 Superfortress

View attachment 654747

Yes - I believe the Silverplate mod moved a bulkhead to the atomic weapon would fit, in doing so different bomb bay doors were used

 

[Snautzer01]

That is what i am looking in to. I think (!) the doors became too big to closes the usual way. Hence the hydraulics i think. So was is a Winker Winkler type bomb bay?