Heinkel He 177 With tandem DB605s

[tomo pauk]

Looks like it was 'just' 480 km/h (~300 mph) per the datasheet. Clean aircraft, 25.2 tons, With two guided missiles it was 440 km/h.

The dana sheet posted here shows up to 490 km/h, with 5% of power loss due to installation of flame dampers: sheet

Heinkel was giving up to 550 km/h for the He-177A-3 (DB 601) on the other hand.

 

[BiffF15]

I didn't realize that the props rotated in opposite directions.

Cheers,
Biff

 

[Zipper730]

Looks like it was 'just' 480 km/h (~300 mph) per the datasheet. Clean aircraft, 25.2 tons

298.3 mph @ 55,556.5 pounds...

With two guided missiles it was 440 km/h.

273.4 mph @ 60,161.2 pounds...

The dana sheet posted here shows up to 490 km/h, with 5% of power loss due to installation of flame dampers: sheet

304.5 mph...

Heinkel was giving up to 550 km/h for the He-177A-3 (DB 601) on the other hand.

341.8 mph...

Other than the flame-dampers, why the discrepancies in speed?

 

[Shortround6]

I didn't realize that the props rotated in opposite directions.

Cheers,
Biff

Don't know if you are aware of it or not but the each engine of the pair could be de-clutched and the prop run on just one of the engines. How often this was actually done I have no idea but the complications to the gear box would be substantial.
I have no idea if the goal was extra long range by running on two of the 4 engines or extra safety by being able to shut down a damaged/defective engine and yet keep the prop turning and providing at least some thrust.
I also have no idea of the restart procedure (or if there was one). Use normal starter motor or just clutch the dead engine? that would be quite a shock to the system.

 

[tomo pauk]

The DB-610A was turning in opposite direction vs. DB-610B; 'handed engines' as the Americans speak.

...
Other than the flame-dampers, why the discrepancies in speed?

Manufacturer's figures considerably greater than user's? Happened many times before and after the He 177, eg. the P-39, P-40, P-63, Spitfire were sometimes slower than the 'book speed'. Fw 190A2/A-3 was, per mfg, supposed to do far better than what it did in real world. The Soviet aircraft were also well known for serial examples falling well behind vs. what prototypes attended, especially fighters and the Il-2.

 

[BiffF15]

Don't know if you are aware of it or not but the each engine of the pair could be de-clutched and the prop run on just one of the engines. How often this was actually done I have no idea but the complications to the gear box would be substantial.
I have no idea if the goal was extra long range by running on two of the 4 engines or extra safety by being able to shut down a damaged/defective engine and yet keep the prop turning and providing at least some thrust.
I also have no idea of the restart procedure (or if there was one). Use normal starter motor or just clutch the dead engine? that would be quite a shock to the system.

Pretty leading edge technical stuff back in the day. I would think they would have built something that has a restart procedure that wouldn't destroy another much needed component. I would expect it was restarted in the decoupled / declutched mode using a starter. However, in combat all bets would be off as survival comes above tech orders / pilots operating handbook...

Cheers,
Biff

 

[Zipper730]

Manufacturer's figures considerably greater than user's? Happened many times before and after the He 177

Okay, I gotcha.

Do you know how much weight did the He-177 gain from when it was initially proposed around level-bombing with the strength to perform shallow/moderate-angle glide-bombing, to when the aircraft's specifications were changed to require a dive-bombing capability, to when the aircraft actually entered service?

 

[Denniss]

Heinkel claimed the 550 km/h in the "Kurzbeschreibung He 177A-3" dated 12/42. This statement is flawed as it claimed this speed with 30min engine power at engine FTP of 6.8 km which is completely wrong as the FTH was 5.8 km (in the same doc just one line above).
The speed graphs in the doc are likely 50 km/h too far right and 800m too high for the given engien power. 520-530 km/h may have been possible at maximum engine power

 

[Zipper730]

Heinkel claimed the 550 km/h in the "Kurzbeschreibung He 177A-3" dated 12/42. This statement is flawed as it claimed this speed with 30min engine power at engine FTP of 6.8 km which is completely wrong as the FTH was 5.8 km (in the same doc just one line above).

That's a big gaffe...

520-530 km/h may have been possible at maximum engine power

I thought all maximum speeds are based on full power?

 

[Denniss]

Full power, often termed as 100%, was most often not maximum engine power but a ~30 minute rating.

 

[Zipper730]

The requirements for the He-177 seemed to dictate a 500 kph requirement: Was this at the 100% setting or the 30-minute rating?