What exactly 'was' the combat radius of the He 177?

[BraselC5048]

First off, I'm well aware that 'range' can vary a heck of a lot, depending on what the precise definition and assumptions used are. And 'combat radius' introduces its own set of assumptions. For example, i was able only by cross-referencing 3 different tables that the definition of combat radius used for the DH 103 Hornet was with 15 minutes of combat power and 100 miles of reserves. I'm also quite familiar (from flight sim experience) of the operation of civil airliners using turbo-supercharged large radials (R-3350's and Wasp Majors).
Which comes to the question of what the (or perhaps a realistic "a") practical combat radius (for a strategic bombing mission) of the He 177 was. I've seen two figures given (without cites), 945 mi and 745 mi. I also have a range figure from 'Winkle" Brown's book of 3100 mi range with two 1400 kg 'Fritz X' guided bombs. That's apparently a decent bombload, and it also covers payload/range (the only figure I've found that includes the bombload assumption), and seems definitive for range with that bombload, but I'm finding it hard to reconcile with a combat radius of under 1000 mi, since I can't seem to figure anything that would account for a full thousands miles of range. (And I don't have figure for the effects of max cruise and combat power anyway.)

 

[drgondog]

The combat radius is dictated by the mission ( escort, in which optimal cruise speed is tailored either by flight path (i.e Essing) or modified cruise settings to match bomber speeds - or a compromise.

For a WWII conventional bomber (B-17, Lancaster, He 177, Ju 88) in which a typical mission is defined by trading payload (fuel, crew, bomb load, ammo load) is traded for range a set of parameters need to be assessed. That said,
typical combat radius planning charts are conceptualized and then refined by flight tests so that specific fuel consumption as a function of MP, RPM and altitude charts can be documented along with a set of assumptions.

Internal fuel for the mission, payload, external drag items, cruise speeds as a function of GW and engine settings are key calculation parameters.

During the design phase, mission profiles are often stipulated as a spec and could be described as "Start engines, taxi/take off/climb to altitude, cruise to target, bomb - for the max Gross take off condition for a bomber; then return cruise at a specific altitude calculated at a lower gross weight and even engine settings, loiter for 30 minutes, descend for landing and land with X minutes of internal fuel remaining".

The universal key to mission planning was the mission characteristics which could be expected at the extreme of the planning horizon. For an escort fighter it could be "Drop external fuel tanks/go 100% internal, fight for 5 minutes at WEP, 15 minutes at MP, cruise at 25,000 feet at optimal cruise settings for range at specific altitudes, loiter for 30 minutes, and land with 15 minutes internal fuel remaining".

Then operational and planning details can alter the mission Profile. If a Mustang Group is tasked to go straight to the target and pick up their assigned bombers on the IP, escort them over the target, escort them halfway home - thaey may be cruising at 300mph TAS but because the bombers are doing 210mph TAS, the fighters are not traveling nearly as far in the direction of home because they are Essing around and over the bombers to keep pace - so the planner has to take that factor into account.

 

[drgondog]

So, back to the He 177. Grab your flight tests which detail various cruising speeds as a function of GW (internal) plus any external stores for the Cruise profile. Based on Flight tests you will have the climb performance as a function of gross weight and fuel consumption to get from take off to climb to altitude. Then another set of fuel consumption to speed calcs drive the optimal cruise speed/fuel consumption for cruise to the target. Then look at flight tests for the 'empty bomb load' characteristics with expected gross weight to include internal fuel remaining - and re-calculate elapsed time to return as a function of altitude and optimal cruise settings, Then look to a safety margin for bad weather or headwinds, then a landing with a fuel reserve of your choice.

Additional calcs include a.) time to warm up, taxi, take off, assemble into a formation - before climbing to cruise altitude, b.) different cruise speeds and fuel consumption based on increased drag of external fuel tanks/bomb loads, c.) increased loiter time of large formations breaking down for approach and landing.

Weather, Tail winds, cloud cover over base of operations are also factored in to tailor a mission plan.

 

[BraselC5048]

Exactly. My main problems are that I don't know exactly which allowances need to be made, and more importantly I don't have any fuel consumption data or detailed range data anyway.

Mostly I'm concerned about "could a large formation launch a bombing raid at a target at 'X' distance with adequate fuel reserves and carrying an adequate bombload." (I'm considering the bombload of a B-17 as minimum adequate, which IIRC was around 4000 (Or might have been 8000) pounds or so, I'm going with 3000 kg as enough.) My target distance is mostly of the "did it actually have the range to reach Soviet war industry past the Urals anyway" type, and apparently 'Tankograd" is ~950 miles from the nearest territory that the Germans held for all of 42'. (Assuming the bomber had been ready by then.)
It would seem to me that a 3100 mi max range with ~3000 kg of bombs would translate into at least a 1000 mi combat radius, so such a raid would be possible, although I'm rather hoping I'm wrong.

Likely would be a good idea to look at mission profiles for B-17 raids and extrapolate from there.

 

[tomo pauk]

There is a table here: link. From this thread: link. For DB 610 engines.
Going after the data from the table, max range is 4400 km max, with 11100L of fuel and 1 ton of bomb load, economical cruising, no fuel allowances. With 2 missiles, 9560 L of fuel, cruise on max continuous power, (with allowances?) was 2660 km.
Radius? Rough rule of the thumb is that radius is 1/3rd of the range, so we are looking at ~900 to ~1450 km worth of radius, depending on payload and fuel carried, as well as cruise power settings and allowances.

 

[davebender]

Which variant?

 

[BraselC5048]

Thanks for the documents, the only problem is that (as I should have expected, but somehow didn't realize) they're in German. I'll take your word for the translation. What's the range figure for 2 missiles and economy cruise, if it's there at all? (I can't read a word of German, nor type in into a translator and expect results for technical terms (and I don't know how to type in German, and can't quite make out all the letters anyway.))

I found the flight planing documents for a B-17, (G?), which at 6000 lb of bombs (about the same as 2 1400 kg-ish missiles) also had a 3100 miles theoretical range. (Which does not make the He 177 look good.) It's actually standard propliner (Piston engined airliner) stuff, and I certainly know how to use that.

The B-17 variant in the docs could fly a 1025 miles mission, with 6000 lb of bombs, still air with 7% reserves. (Assumptions include ground fuel given in the charts, 20 min at each end as first plane to take off/last plane to land loiter, 15 min to form up and regular climb.) The normal civil requirement was (I 'think') 15% reserves. If an engine was lost over the target, it would have EXACTLY the fuel needed to return to base, (Perhaps a little more), assuming still air and no headwinds. Reducing to 925 miles to the target improves reserves (no engine failure) to 18% or so.So it seems 1/3rd is roughly right.

(One somewhat alarming thing for a 4 engined combat aircraft - no "2 engine out" cruising table. I have a feeling that losing 2 engines would result in a B-17 being unable to stay aloft. All the great 4 engined piston airliners could stay in the air on 2 engines, although they also had 2800+ HP continuos power per engine at max cruise.)

I also would assume that compared to a B-17, a He 177 would be in much more trouble if it lost an engine due to the cupeled engines, likely requiring shutting down 2 engines rather than one (or simply losing two since they were right next to each other, assuming a cannon shell would take out both.) Could it even stay aloft in the event of losing the engines on a nacelle?

 

[tomo pauk]

With 2 missiles, the range is 3270 km on economical cruise.
On mean weight (26000 kg) and two operative 'half engines' ( 'mit 2Motoren' caption, one on easch side), the He-177A-3 was supposed to mantain height above ~3.7 km: graph
The graph also notes the climb rate with 3 'half engines' operating ('mit 3Motoren' caption), it should mantain height above ~7.7 km in that case, again for 26000 kg weight.

I don't think that anyone would've fancied flying the He 177 with both engines on one of the sides inoperative

 

[Shortround6]

The two engine out scenario depends a lot on which two engines. Losing both engines on one side makes things a lot more iffy than losing the outer engine on each side. A lot more rudder drag trying to correct for the asymmetrical thrust. Losing an inner engine on one side and outer on the other is in between.

The He 177 was supposed to be able to disengage the coupled engines from each other. There were clutches between the engines and the gear box. Identifying which engine of the pair was the defunct engine may be easier at times than at other times (smoke belching from appropriate exhaust pipe/s?) Getting the appropriate pitch on the propeller of the damaged pair for least drag/most thrust compared to the prop on the undamaged pair may be harder to do.

 

[drgondog]

A B-17, by dumping ball turret, ammo, waist guns, etc - often
made it home on two good engines (1 each side)

 

[Shortround6]

They may have made it home (on rare occasions) with 2 engines on one side by dumping even more stuff, motivated crew with tools
This also depends on other damage to the aircraft, large holes or flaps of metal in the air stream creating more drag, weather/temperature (cool air provides more lift and may help engines being pushed past the "normal" settings and so on.
It might even depend on how high the plane was (and where) when the 3rd engine quit. Plane descending at 200fpm from 20,000ft is flying for an hour and 40 minutes.

 

[davebender]

B-17, by dumping ball turret, ammo, waist guns, etc - often made it home on two good engines

Typically they started at about 25,000 feet and lost altitude for the entire distance home. If they weren't attacked again enroute as such an aircraft was an easy target.

 

[yulzari]

Typically they started at about 25,000 feet and lost altitude for the entire distance home. If they weren't attacked again enroute as such an aircraft was an easy target.

Ironically wise He177 pilots in the 1944 blitz climbed to maximum altitude over France and slowly lost height as the approached their target to maximise their airspeed. IIRC a figure of nearly 400 mph airspeed was quoted somewhere.

And yes children. Britain was being bombed in 1944, and shelled, and hit by V1s and rocketed with V2s and coastal shipping was being attacked by the German navy.

 

[parsifal]

Not a great source, but Green says when configured foir anti shipping role with a typical long range load out of 16 x 110 SC 50 lb bombs, 4 x 551 SC 250 bombs or 2 x 1102 lb SC 500 bombs, the range (I think one way) was 1988 miles with 2820 imp gallons of fuel. The medium and short range load outs were a lot heavier , but the range also came down a heap.. Ferry range could be as high as 3480 miles.

 

[wuzak]

Smith and Creek, Heinkel He 177 Greif, Heinkel's Strategic Bomber, have the He 177A-5 with a maximum range of 5,500km (3,417 miles) with two Hs 293 missiles, and 5,000km (3,107 miles( with two Fritz X guided bombs.

 

[Zipper730]

I got a message from an online friend regarding the He-177's performance. I was asked several questions which included things I had already asked before, though in greater detail, so I think I will ask on another thread.