My understanding was that the Vulture was prone to overheating and fire.
The Vulture has 5 issues:
1. If upper and lower crankcase halves aren't kept in exact alignment, the main bearings aren't aligned = crankshaft starved for oil = seized. Keeping aligned in production environment is nearly impossible. Solution larger dowels ("cheeses") between crankcase halves and precise tightening sequence.
2. Vulture used 2 cooling pumps (one for each 1/2 of the engine). Because of the cooling piping design, one pump or other would tend to cavitate and stop pumping. No cooling medium = engine overheats and seize. Solution: Balance pipe between the pumps and there were no longer cavitation issues.
3. Connecting rod bolts have 2 issues: When connecting rod fails, it tends to punch hole in side of block. Oil pours out, flowing down onto red hot exhaust.
a. Bolts have poor heat treating and don't meet strength requirement. Solution: More stringent heat treatment
b. Connecting rod uses 2 different lengths of bolts. The longer bolt stretches more before it provides the same clamping force, so you need 2 different tightening torques. If you tighten the short bolt too much, it fails, if you tighten the long bolt too much the cap isn't properly held in place. Solution: Go/No Go gauge to check the bolt stretch. If short bolt is stretched too much you can't push the gauge in (No Go) and you have to unbolt, throw the ruin bolt/nut into recycling and install new bolt, nut and torque correctly.
4. Rolls Royce tries battery/coil/points/condenser instead of magnetos. Dead battery/failed coil/points/condenser = no spark. Solution replace with magnetos.
But by the time RR has diagnosed the issues and resolved them, the Vulture has a bad reputation. Last of the Vultures were getting 150 hours before overhaul; which would be a good as another other UK engine of the time period.
5. The Vulture I was designed for 1,750 hp on 87 octane fuel. 100 octane fuel is now available in quantity. Vulture needs be redesigned for 2,500 hp:
a. Larger carburetor
b. Larger supercharger; stronger supercharger gears (and we haven't got into 2 stage)
c. Stronger pistons
d. Stronger connecting rods
e. Stronger crankshaft
f. Stronger crankcase
g. Stronger reduction gear
h. Larger cooling pumps
and I've probably missed something.
At the same time, RR has the same issue with the:
Peregrine I - they just bin this...if you want 1,200hp get a Merlin I, if it doesn't fit in your airplane - that's your issue, not RR problem.
Merlin I - which they are redesigning as Merlin XX to support 1,500+ hp.
Griffon I - they bin the initial design and take what they've learned to create Griffon IV, 1,750+ hp.
Vulture...RR bins it; at the time, there is no airframe requiring a 2,500 hp engine.
Back to the Manchester.
Not only is RR having issues with their engine, Avro is having issues with their airframe:
1. It doesn't want to fly on single engine (one a day in Tampa Bay comes to mind with B-26).
Aside: For a plane, the designer needs to compromise; he needs enough fin/rudder area for pilot be be able to control the airplane just after take off. But he wants to keep it as small as possible to minimize drag. For a twin, he has 3 choices.
A. Single fin/rudder: Advantage: Out of propwash, so minimizes drag during cruise. Disadvantage: Out of propwash; issue if an engine fails... So, single fin/rudder needs to be larger, which has issue with fuselage twisting (less of an issue with tail dragger as fuselage needs to be strong for other reasons)
B. Twin fin/rudder: Advantage: In propwash, if an engine fails, there will still be rapidly moving air across at least one fin/rudder. Disadvantage: In propwash all the time; adds drag during cruise.
C. Triple fin/rudder - central fin and small twin fin/rudders. Avro also made the tail plane narrow - which sounds like great idea - twin fin/rudders are mostly out of the propwash reducing drag during cruise. The problem: the Manchester needs to yaw a little before the fin/rudder gets into propwash, increasing drag... And the last thing you need when the critical engine fails when you are just clearing the engine of the runway at max take off weight is a little drag.
Solution increase tail plane from 22' to 33' increase size of fin/rudders
2. The plane is overweight...Solution addition wing area (wingspan increased from 90 to 95' (more drag/slower, but safer; again sounds like B-26)