Twin Engine Fighters

[Shortround6]

A problem with the 109Z is that was kind of either/or. Either it was a single seat seat twin engine fighter with somewhat adequate fuel (a tank went were the cockpit was in starboard fuselage) or it was a two seat (night fighter?) twin engine plane with dismal fuel supply.

 

[pbehn]

When I read a pilot report on the F-82, all participants noted an unusual characteristic that everyone liked. To the pilot, it seemed as if the aircraft were rotating around his cockpit when it rolled. To the non-pilot, it seemed opposite. That is, both crew felt as though the aircraft were rolling around their own cockpit. So the issue you perceptively rasied above didn't occur.

That is NOT to say the Bf 109Z or any other "Siamese Twin" would have the same results. Because one twin-fuselage-fighter didn't have the issue doesn't mean others wouldn't have it. It would probaly have to be investigated for all such twins before any blanket statement could be made and even then, you can't be sure the next one wouldn't exhibit the problem.

Greg...I can imagine that as a sensation, like sitting on a train when the train next to you moves forwards you think you are moving backwards. I meant the distance from the seat to axis of turn, the bigger that is the larger the actual G force in a roll, I wouldnt know how to convert roll in degrees/second to "G".

 

[GrauGeist]

A problem with the 109Z is that was kind of either/or. Either it was a single seat seat twin engine fighter with somewhat adequate fuel (a tank went were the cockpit was in starboard fuselage) or it was a two seat (night fighter?) twin engine plane with dismal fuel supply.

The Bf109Z (based on the Bf109F) and the proposed Me609 (based on the Me309) both were always intended to be single-seat, the cockpit being on the port fuselage. Each type was to have been either a heavy fighter or a fighter/bomber.

The "Z" idea kept coming back to Messerschmitt, as there were proposals on paper to make a "Zwilling" from the Bf109G and the Bf109H. Like the Me609, those proposals never left the drawing board.

It would jave been interesting to see how the Bf109Z performed, but I suspect that it may have had some handling issues that were learned during the P-82 development. Once they installed counter-rotating engines, the P-82 was a winner. I have never read anything about Messerschmitt intending to install anything but a pair of standard DB601E engines.

 

[GregP]

Converting roll into g is not difficult, but they didn't roll fast enough for that to be an issue.

In Physics, centripetal acceleration is given by: ac = v^2 / r, where ac = centripetal acceleration, v = tangential velocity, and r = radius, with consistent units.

But to get to some significant acceleration would require quite a roll rate, sustained over some revolutions. I susect they'd usually not roll more than once and, more ofdten, not more than maybe 120°, followed by a good pull to escape or attack. If they had to, they weren't flying right.

 

[T Bolt]

The P-82 wasn't really a 'twin' Mustang. The fuselages were not at all like the P-51D which everyone knows, but more like the light weight P-51H, although they were not truly P-51H fuselages either but a compleatly new assembly, considerably longer than any other Mustang. I tend to think that this lengthening of the fuselage would be needed in any of these twin fuselage fighter types to compensate for the longer wingspan.

 

[GregP]

For those of you who think a two-cerw version had dismal range, recall that on 27 Feb 1947, Col. Bob Thacker flew a P-82B nonstop from Hawaii to New York, a distance of 5,051 miles (8,129 km). The aircraft carried a full internal fuel tank of 576 US gallons (2,180 l; 480 imp gal), augmented by four 310 US gal (1,173 l; 258 imp gal) tanks for a total of 1,816 US gal (6,874 l; 1,512 imp gal). Also, Colonel Thacker forgot to drop three of his external tanks when their fuel was expended, landing with them in New York. It averaged 347.5 miles per hour (559.2 km/h).

The normal range with a crew of 2 was 2,350 miles or just short of London to Berlin and back twice.

I call it a "Twin Mustang" bacause that is the official name, not because of the parts it was made from.

 

[Shortround6]

P-82 was a bit of a special case as they found room for slightly more fuel than two separate Mustangs using rear tanks.

In part because they didn't keep four landing gear legs and didn't try to carry twice the gun armament of a single Mustang.

 

[T Bolt]

Sorry, the point I was trying to make was that the P-82 wasn't just to mustangs bolted together like the 109Z, But an almost completely new aircraft

 

[GregP]

I've never SEEN a thread on the Fw 187 in which many people didn't claim the engine intended all along was the DB 601. Of course, if you actually LOOK at the Fw 187's built, how many HAD the DB 601? They never seem to stop and think about that much.

 

[GrauGeist]

I suspect Willy kept the original landing gear intact on the Bf109Z for two reasons:
First, the original landing gear wasn't robust enough to support the full weight of the dual fuselages, additional armament and full load-out if it were "halved"

Secondly, modifying the landing gear to have half of the main gear under each fuselage would require additional labor and Willy intended to keep as much equipment "off the shelf" as possible.

It seems that Messerschmitt never did design a main gear that was completely trouble-free...

 

[redcoat]

I think we covered that already, but if not, it didn't stay in service long and it's combat success seems quite hard to document. Lack of information about it makes me think it didn't do all that well. It is possible it did but, if so, why is it so hard to find out about? It wasn't used by many squadrons because there weren't all that many Whirlwinds built ... 114 or 116 total, including 2 prototypes. That won't go very far equipping an Air Force.

The Whirlwind was in front-line operational service from December 1940 until June 1943 (a remarkable length of time for a single mark of an aircraft in WW2), where it was usually used in a low level strike and escort role over Northern France.
It seems to have had a reasonably successful career, and remained popular with it's pilots until it's retirement.

 

[Shortround6]

I've never SEEN a thread on the Fw 187 in which many people didn't claim the engine intended all along was the DB 601. Of course, if you actually LOOK at the Fw 187's built, how many HAD the DB 601? They never seem to stop and think about that much.

Greg, I am willing to concede to the FW 187 fans that it was designed for some sort of DB 600 engine and the prototypes got Jumo 210s because DB couldn't supply ( or the German Air Ministry would not release/allocate) the DB 601s. Bf 110s couldn't get enough DB 601s in 1938 and early 1939. About 1/4 to 1/3 of the Bf 110s used against Poland used Jumo 210 engines. Every Fw 187 prototype with DB engines in 1939 is a Bf 110 with Jumo 210s
However I have serious doubts about the performance of a service FW 187 using normal DB 601 engines compared to the hot rod specials using surface cooling as installed in the V6 prototype. It undoubtedly would be better than the the Jumo powered versions though.

I have few questions about the armament in regards to timing.

 

[kool kitty89]

Greg, I am willing to concede to the FW 187 fans that it was designed for some sort of DB 600 engine and the prototypes got Jumo 210s because DB couldn't supply ( or the German Air Ministry would not release/allocate) the DB 601s. Bf 110s couldn't get enough DB 601s in 1938 and early 1939. About 1/4 to 1/3 of the Bf 110s used against Poland used Jumo 210 engines. Every Fw 187 prototype with DB engines in 1939 is a Bf 110 with Jumo 210s
However I have serious doubts about the performance of a service FW 187 using normal DB 601 engines compared to the hot rod specials using surface cooling as installed in the V6 prototype. It undoubtedly would be better than the the Jumo powered versions though.

I have few questions about the armament in regards to timing.

I think the V5 was the only one tested with an actual DB 601, but may or may not have used surface cooling (did use some sort of experimental cooling system, pressurized/evaporative but may have used a conventional radiator like the later pressurized DB engines). Performance information is limited on that prototype, as is overall configuration, but from the bit I've seen it managed better than the earlier surface-cooled DB 600 powered prototype. (which itself seemed to have a very limited critical altitude and achieved that ~395 mph figure at low level)

I agree it's unlikely that DB 601A equipped, fully armed (single or two seat) production Fw 187s would have managed similar speeds in either case, but performance significantly beyond the Jumo 210G seems logical, especially above the 210's critical altitude. I could see a light, unarmored prototype version (even a two seater) with conventional radiators and DB 601s still exceeding 400 mph at altitude, but far less likely when weighed down with operational equipment. (DB 601Ns or Jumo 211Fs might have managed it)

But most of that's academic anyway, the bigger point probably would have been at least moderately faster than all 1940 opponents and likely much better climbing, though roll rate might suffer with the heavier engines. (even with Czech Hispano 12Ys it might have out-run 109s and spitfires at altitude and much more so in the 12Y's best atltitude range)

It would have been a poor replacement for the Bf 109E in most respects due to overall cost (and the 109's ground handling issues AND short range could/should have been addressed in more cost-effective ways than needing a total replacement), but compared to the Bf 110, the Fw 187 with either set of engines seems much more useful in every practical circumstance except for cannon drum reloading. (more MG-FFs seems the simplest solution there) The Fw 187 should NOT have been in direct competition with the Bf 109, though.


Having counter-rotating props would be nice (and possible with 12Ys) but DB and Jumo seemed to lag in that regard.


From the story as far as I know it, it seems like Udet could have been more of a driving force behind the 187, particularly for pushing it beyond the constraints of the Zerstorer requirements. He had misgivings over its potential maneuverability, but having him test fly it seems to be a potent solution there. That never seems to have been arranged, unlike Heinke's various occasions of having Udet test his aircraft, but perhaps Tank (or others at Focke Wulf) were concerned Udet might crash or otherwise damage the prototype given his track record.

Honestly, in this regard, using the Jumo 210 would have been an advantage. The smaller size and weight would have maximized the maneuverability of the aircraft and made it appear more favorable than if loaded with DB 601 or Jumo 211 engines.



As far as armament goes, as a heavy fighter/interceptor, 6 MG FF cannons would have been fairly close to the weight/bulk of the P-38E or Whirlwind's armaments and lighter than the P-38D's (and any others using the earlier 37 mm cannon + 4 .50 browning arrangement). Some bulges to fit all the drums might have been needed, but it hardly seems an unreasonable configuration. (adding 2 more MG FFs to the existing Fw 187A-0 armament might have been a quicker modification at that point though, 4 MG FFs and 4 MG 17s would have been plenty useful at the time and more than double the Bf 109E's firepower -lack of synchronization + concentration of fire)

 

[pbehn]

In Physics, centripetal acceleration is given by: ac = v^2 / r, where ac = centripetal acceleration, v = tangential velocity, and r = radius, with consistent units.

But to get to some significant acceleration would require quite a roll rate, sustained over some revolutions. I susect they'd usually not roll more than once and, more ofdten, not more than maybe 120°, followed by a good pull to escape or attack. If they had to, they weren't flying right.

I am not an expert but centripetal forces act from the inside of a circle outwards. The forces I am talking about are the difference between sitting at the centre of a rolling aircraft and those experienced a few metres away, like flying an AC while sat on the wing. That is kicking one pilot in the ass to turn and having the other hanging on his staps rather than trying to throw them out of the side of the aircraft. The equation therefore must be a function of radius and degrees/second but I have no idea whether an aeroplane rolls at a constant rate, gets progressively faster, to me there must be a transition between level flight and maximum roll. A plane with two obvious centres of mass connected so as to only one axis of rotation would behave very strangely, or I think it would any way.

 

[pbehn]

Idea for a twin engined fighter:-

A twin engined fighter mosquito sized with a nose armament like the chin turret on a late B17 operated by the co pilot when in fee combat or locked straight ahead and operated by the pilot ....meaning even if up against a tighter turning AC it could get a shot on target.

 

[fastmongrel]

Idea for a twin engined fighter:-

A twin engined fighter mosquito sized with a nose armament like the chin turret on a late B17 operated by the co pilot when in fee combat or locked straight ahead and operated by the pilot ....meaning even if up against a tighter turning AC it could get a shot on target.

The 2 gun Bendix chin turret weighed over 700 pounds with ammo. Thats a lot of weight for not much firepower.

 

[GrauGeist]

Idea for a twin engined fighter:-

A twin engined fighter mosquito sized with a nose armament like the chin turret on a late B17 operated by the co pilot when in fee combat or locked straight ahead and operated by the pilot ....meaning even if up against a tighter turning AC it could get a shot on target.

It was proposed by Armstrong Whitworth in the form of the AW.34 in response to an Air Ministry request. After consideration of the submissions, the Air Ministry abandoned the idea, revised the requirements and ended up with the Boulton Paul Defiant.

As history showed, turret aircraft didn't fare too well when put into combat.

Here's the AW.34 concept:

 

[kool kitty89]

The AW.34 reminds me a bit of Bell's YFM-1 Airacuda ...

Rather like the failed Kampfzerstorer concept, Bell would have been much better off going the route Messerschmitt did with the Bf 110, or even Bristol with the Beaufighter's reloadable cannons, less than half the crew and around 2/3 the size and a similar offensive armament. It's no P-38, but it makes a hell of a lot more sense than the YFM-1.

Idea for a twin engined fighter:-

A twin engined fighter mosquito sized with a nose armament like the chin turret on a late B17 operated by the co pilot when in fee combat or locked straight ahead and operated by the pilot ....meaning even if up against a tighter turning AC it could get a shot on target.

Wasn't that part of the logic behind the 'no allowance' upward angled cannons in the F.9/37? (that and the ability to fire at aircraft from below while still at horizontal attitude, but not in the extreme upward angles German Nightfighters used)

It'd be interesting to see the gunsight arrangement for that.

Seems useful for boom and zoom tactics too, with the ability to actually follow on the OUTSIDE of a turn for a short period, still line up a good deflection angle, and then break off and zoom away. (with the Whirlwind's high wing loading and good roll rate, that sort of arrangement seems favorable there as well)

 

[GregP]

C'mon, the YFM-1 was not a fighter ... it was an airborne fighter SQUAD of guys.

Great camaraderie in the roaring 30's ... if altogether useless. It DID help develop the Allison V-1710, but it was sort of like going hunting with an accordion as a weapon. You might bludgeon something to death with it (likely not) but, if you DID, it wasn't going to be pretty and NOBODY was going to be satisfied except Larry Bell.

Wonder if each one of those pods had a relief tube? Maybe they could jettison waste byproduct on the enemy and corrode their airframes before they got back home ... sure as HELL would hate to bail out of a pod with the trusty Allison going at 2,700 rpm or more. Heck, I'd pretty much hate if the engine was at idle or even stopped dead. A stopped prop would be about just as bad as turning prop.

That's when you KNOW you got it wrong.

It's sort like ... would you be more offended if someone said you had the morals of an alleycat or you DIDN'T have the morals of an alleycat?

 

[kool kitty89]

Hey, the Fw 57 is categorized as a fighter ...
https://en.wikipedia.org/wiki/Focke-Wulf_Fw_57

Those pusher engines with special extension shafts would have been more interesting to see used for actual attempts at drag reduction on a high speed design.

Like if some of the P-39's design concepts were applied to a twin engine heavy fighter -much lower drag wing for one, even considering the size difference, sleek fuselage, tricycle gear (easier and more practical on a twin anyway, especially a pusher -the YFM-1 being a taildragger was just one more out of place oddball design trait), concentrated centerline armament (again, easier on a twin), canopy with good all around field of view (XP-39 was better than the P-39 there), and that unusual engine arrangement to improve streamlining and facilitate specialized armament (true for the pusher arrangement too, except keeping the cannons on the centerline would make more sense). And of course, the twin engine arrangement makes turbochargers and intercoolers far easier to implement. (pusher prop nacelles might have actually allowed a lower drag arrangement there than Lockheed managed on the P-38 ) Counter rotating props also tend to make spins nearly impossible or close to it so long as both engines are working properly and at the same throttle and RPM settings (no asymmetric torque or thrust).


The YFM-1 though ... really a bizarre aircraft to see get that far into development.