Some Aircraft seem to be much easier to fly than others when doing low level high speed passes. One of the nice things about opposite rotation of the engines is that there is no noticeable lateral or directional trim changes. There is also quite a lot more acceleration.
Did lots more tuning on the P-38J. Some of these edits were quite radical and I am still not all that close to final yet.
One of the funniest things I encountered was braking too hard and flipping (!) the aeroplane.
That wasn't hard to fix, but it was an interesting surprise to flip an aeroplane with a nose wheel.
The Flight model I was working on had three fuel tanks per side:
A 90 Gallon Main Tank behind the main spar of the wing.
A 60 Gallon Reserve Tank ahead of the main spar.
A 55 Gallon Tank in the leading edge of each wing outboard of the engines.
I came across an earlier version of the AIR file (from about 2000 or so) and noted that the model I was trying to build was a P-38J-10.
The early models of the P-38, without the chin scoops, had their intercoolers built into the outboard leading edge of each wing.
This was quite an inefficient setup with the supercharger in the middle of each boom piping charge air out to the wing tips before it went into the engine.
The leading edge intercoolers were efficient for streamlining, but also didn't cool the air that well before it went into the engine. This was the main limitation to running the engines at higher power settings before detonation would start.
With the J model, the intercoolers were moved under the engines next to the oil coolers. That greatly increased the maximum speed because although the airframe drag was higher, the engine power was much higher.
At some point, fuel tanks were installed where the intercoolers were, but those fuel tanks were not present in the J-10 model.
Another feature that was not present in the early J models was the dive brake under each wing to aid recovery in a high speed dive. In trying to add in some compressibility effects, I tried quite a few high speed dives starting from around 35000 feet altitude. Many of them ended up as crashes because elevator effectiveness at very high speeds is greatly reduced and the P-38 gains speed in a dive VERY quickly and ghe maximum diving speed is very low. In fact the limit (460 mph IAS at low altitude) is about the same as for a late model Japanese Zero but for very different reasons. (At high altitude it is only 420 mph IAS.)
This is one of the parts I really like about flight sims: Reading about compressibility effects and dive limitations is interesting, but actually "experiencing" and being able to experiment with the effects gives a much better appreciation of how things worked.
Perhaps this is a bit circular because we try to program in the documented behaviour and then test for the same behaviour.
Current Performance:
1417 HP @ 500 ft for 344 mph
1477 HP @ 25,000 ft for 421 mph
Actual Maximum speed is 427 mph @ 22,500 ft
Service Ceiling was not tested but should be considerably higher with a bit more engine power and less fuel.
Lots more left to tune. Hopefully I can figure some of it out.
- Ivan.
Did lots more tuning on the P-38J. Some of these edits were quite radical and I am still not all that close to final yet.
One of the funniest things I encountered was braking too hard and flipping (!) the aeroplane.
That wasn't hard to fix, but it was an interesting surprise to flip an aeroplane with a nose wheel.
The Flight model I was working on had three fuel tanks per side:
A 90 Gallon Main Tank behind the main spar of the wing.
A 60 Gallon Reserve Tank ahead of the main spar.
A 55 Gallon Tank in the leading edge of each wing outboard of the engines.
I came across an earlier version of the AIR file (from about 2000 or so) and noted that the model I was trying to build was a P-38J-10.
The early models of the P-38, without the chin scoops, had their intercoolers built into the outboard leading edge of each wing.
This was quite an inefficient setup with the supercharger in the middle of each boom piping charge air out to the wing tips before it went into the engine.
The leading edge intercoolers were efficient for streamlining, but also didn't cool the air that well before it went into the engine. This was the main limitation to running the engines at higher power settings before detonation would start.
With the J model, the intercoolers were moved under the engines next to the oil coolers. That greatly increased the maximum speed because although the airframe drag was higher, the engine power was much higher.
At some point, fuel tanks were installed where the intercoolers were, but those fuel tanks were not present in the J-10 model.
Another feature that was not present in the early J models was the dive brake under each wing to aid recovery in a high speed dive. In trying to add in some compressibility effects, I tried quite a few high speed dives starting from around 35000 feet altitude. Many of them ended up as crashes because elevator effectiveness at very high speeds is greatly reduced and the P-38 gains speed in a dive VERY quickly and ghe maximum diving speed is very low. In fact the limit (460 mph IAS at low altitude) is about the same as for a late model Japanese Zero but for very different reasons. (At high altitude it is only 420 mph IAS.)
This is one of the parts I really like about flight sims: Reading about compressibility effects and dive limitations is interesting, but actually "experiencing" and being able to experiment with the effects gives a much better appreciation of how things worked.
Perhaps this is a bit circular because we try to program in the documented behaviour and then test for the same behaviour.
Current Performance:
1417 HP @ 500 ft for 344 mph
1477 HP @ 25,000 ft for 421 mph
Actual Maximum speed is 427 mph @ 22,500 ft
Service Ceiling was not tested but should be considerably higher with a bit more engine power and less fuel.
Lots more left to tune. Hopefully I can figure some of it out.
- Ivan.
