Heinkel He 177 With tandem DB605s

[wuzak]

Would the He 177 have been more successful had it used tandem DB 601/5s instead of the coupled version, the DB606/610s?

What I am think here is that the two motors are completely independent driving coaxial propellors. The rear engine could, perhaps, run an extension shaft in the vee of the front engine, in the area where the motor cannon is located. Though this would mean that the rear engine would have its reduction on the engine and the extension shaft would therefore have to be larger.

Would there be difficulties with the control of the prop pitch?

Would similar installation problems occur as for the coupled versions?

 

[tomo pauk]

The coupled engines (DB-606) were troubled because the exhausts were at the lower part of engine nacelle, and that was not mixing well with any oil (and fuel?) that might be leaking down from the engine. The double DB-605s (= DB-610) have had the exhausts better shielded, so the propensity for the fire to start was cured.

The layout you propose is similar to the one used in Ki-64, the Japanese fighter. It was using the power plant system consisting of two copied DB-601s, claimed speed was just under 700 km/h, while employing evaporative cooling.

 

[davebender]

coupled engines (DB-606) were troubled because the exhausts were at the lower part of engine nacelle

I agree. Poorly designed engine compartment will cause problems whether engines are coupled, tandem or single (i.e. early Fw-190A).

However I still don't like coupled engines on a military aircraft as damage to the coupling takes two engines off line. Tandem is more damage resistant and separate engines (i.e. He-177B) are better still.

 

[stona]

Poorly designed engine compartment will cause problems whether engines are coupled, tandem or single

Absolutely and the He 177's was awful.
There were continual leaks of various fluids due to chaffing of pipes and unions as well as problems with electrical insulation.
All this was largely caused by the "sinking" of the engine installation into the wing which severely limited available space.
Cheers
Steve

 

[davebender]

Heinkel He 177 - Wikipedia, the free encyclopedia

Starting with the He 177 A-3/R2, a modified engine nacelle with a new "power system", the Daimler-Benz DB 610, each of which consisted of a pair of Daimler-Benz DB 605s set up to work as one as the DB 606 had been, was used to eliminate the tendency for engine fires.[23] With the introduction of the DB 610 came several improvements including the relocation of the engine oil tank, the lengthening of the engine mountings by 20 cm (8 in), the complete redesign of the exhaust system which also facilitated the installation of exhaust dampers for night missions, and the setting of a power limitation on the engines which resulted in greater reliability. These modifications, supposedly numbering 56 of both major and minor varieties, were successful as far as eliminating engine fires were concerned,

He 177 A-1
First production series
130 built.

He 177 A-3
Sixteenth and subsequent aircraft powered by DB 610 A/B engines.

Total Production Aircraft. He-177A1, He-177A3, He-177A5.
1,094

.....145 production He-177 aircraft had faulty engine installation.
.....For comparison purposes. 209 unreliable Avro Manchester bombers built before switch to reliable four engine Lancaster.

By contemporary standards Germany fixed He-177 engine problems in a timely fashion. However I still don't like coupled engines on military aircraft.

 

[Shortround6]

A problem with the "tandem" arrangement like this is that you get one very looooong engine. Where is the fire wall? where is the back of the engine in relation to the main spar? Is this "V-24" all ahead of the spar, below the spar, the spar runs between the two halfs of the engine with a longer prop shaft from the rear engine? rear engine sits between spars? Spar 'banjoes" around the engine?

Some planes with tandem engines had one engine ahead of the front spar, a loooong nacelle and the 2nd engine behind the rear spar with a pusher prop.

 

[DerAdlerIstGelandet]

A problem with the "tandem" arrangement like this is that you get one very looooong engine. Where is the fire wall? where is the back of the engine in relation to the main spar? Is this "V-24" all ahead of the spar, below the spar, the spar runs between the two halfs of the engine with a longer prop shaft from the rear engine? rear engine sits between spars? Spar 'banjoes" around the engine?

Some planes with tandem engines had one engine ahead of the front spar, a loooong nacelle and the 2nd engine behind the rear spar with a pusher prop.

The DB 606 and DB 610 engines were side by side.

 

[wuzak]

A problem with the "tandem" arrangement like this is that you get one very looooong engine. Where is the fire wall? where is the back of the engine in relation to the main spar? Is this "V-24" all ahead of the spar, below the spar, the spar runs between the two halfs of the engine with a longer prop shaft from the rear engine? rear engine sits between spars? Spar 'banjoes" around the engine?

Some planes with tandem engines had one engine ahead of the front spar, a loooong nacelle and the 2nd engine behind the rear spar with a pusher prop.

I would envision one engine in front of the main spar, and one behind.

Push/Pull may be mor pratical/easier to develop than the coaxial counter rotating propeller system as well.

 

[GregP]

I'd not like a push-pull out on the wing. The purpose of a firewall is to protect what is behind it from fire. If you have one engine ahead of the spar and one behind it, how is the main wing spar protected? What about the aft spar?

Looks like a recipe for disaster to me, but it might work unless battle damage produces a lot of burning oil at just the wrong place. I'd much prefer the He 277 with four engines, whether they be V-12 or radial, but then again, if I had no choice, then I either fly or don't whatever equipment is assigned. In the case of the He 177, there was almost no chance that a unit assigned He 177's had previous equipment of a suitable type since the He 177 was basicaly the only German "heavy" bomber to be built in quantity. At least it was heavy compared with anything else in service. So, the choice would be heavy or not, and that would probably come down to a command decision from above rather than a commander's personal preferences as in the case of top fighter aces staying with the 109 rather than switching to the Fw 190.

 

[tyrodtom]

If you'll look at a cutaway of a He177, you'll notice it has no firewall. The firewall is actually the mainspar.
And the mainspar is so far back in the wing, it must be a monospar wing, with the oil tanks right behind the engine behind the spar, with fuel tanks on each side.

So if you didn't get a engine fire out quick you were courting wing failure.

 

[davebender]

Most heavy bombers had fuel tanks in wing between the engines so I suspect any engine fire not quickly extinguished would result in aircraft loss.

 

[tyrodtom]

You'll have a hard time finding another aircraft without a firewall, except the He177.

 

[Shortround6]

I would envision one engine in front of the main spar, and one behind.

Push/Pull may be mor pratical/easier to develop than the coaxial counter rotating propeller system as well.

It was done and done in the early 30s.

But it is a long engine

one supercharger fed both 12 cylinder units. Separating them and still using a co-ax propeller may present problems. Prop in a P-39 could move about 1 in in relation to the engine. Joints can be fitted to the drive shafts but it is one more thing to deal with.

Mechanical considerations may outweigh the aerodynamic ones. Somebody once claimed the paired engines on the 177 saved about 3% in drag over using 4 separate engines?

If so it seems a poor return on investment.

 

[davebender]

What do you mean by "investment"? Are you suggesting tandem or paired engines cost considerably more then two separate engines?

 

[Shortround6]

I mean that a 3% reduction in drag is a poor return for the time and effort spent designing the gear boxes/drives, large 4 bladed propellers, nacelles and the whole engine installation for what was gotten back. Not to mention the time, effort and lost lives debugging the thing. Put a slightly longer wing on it, use four "normal" engines and props and suck up the 2-3% increase in drag while getting the plane into operational service months earlier.

 

[tomo pauk]

Power plant layout of the Ki-64:

 

[Shortround6]

It CAN be done.

Should it have been done?

It is one way to get a large power plant into a large single or twin seat fighter. You have one fuselage and a pair of wings.

With a 5-7 crew bomber you already have a large fuselage and wing, with tandem engines you have two nacelles ( and hiding the landing gear was always a problem) so you have a lot more drag than a fighter or even the Ki 64 to begin with. The difference between the Fuselage + 2 big engine nacelles and the fuselage + 4 smaller nacelles is a lot closer than the one big fuselage on the Ki-64 and one small fuselage + 2 engine nacelles on a conventional twin.

 

[davebender]

Heavy bombers had such a low priority for Germany that getting He-177 in service as quickly as possible probably didn't have much weight.

Things were different in Britain where RAF Bomber Command absorbed over 12% of the total military budget. In USA too where Ford Motor Company was cranking out B-24s without taking time to work bugs out of the new Willow Run plant and workforce.

 

[spottydog]

Note the rare still of the 177b at 2.54 mark



View: https://www.youtube.com/watch?v=vpAQ1d48Dzg

 

[Zipper730]

Just to retouch on an issue regarding the He-177A

The speed of the DB-610 powered variants I've heard was around 351 mph, though I've heard at least one set of figures that was greatly lower. How fast did the DB-606 and DB-610 variants fly at at maximum speed and cruise speed?

If I recall the requirements were for a minimum speed of 500 kph: Cruise or maximum?