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A lot! Most performance charts start at a baseline, sea level 59F 29.92 air pressure. High temperatures and humidity will make the aircraft perform at sea level as if it was at a higher altitude. Here is a simple calculator. At 100F and 95% humidity your plane will perform as if it was at almost 3,000' MSLSo how much of a difference (in terms of thousands of feet) would 100F and 95% humidity make?
If you were at sea level, those conditions are equivalent to 3365 ft.So how much of a difference (in terms of thousands of feet) would 100F and 95% humidity make?
Assuming a sea level field elevation and an altimeter setting of 29.92, the density altitude at 100 degrees F would be just under 3000'Right i get that, I was wondering what the actual ratios might be, like for the example I gave (100 F and 95 humidity) is it that much? More or less?
The warmer the air, the less the density. The less the density, the less lift can be developed at a given speed. This is a variable that will affect all planes operating in the same airspace in a roughly equal manner. This is also affected by altitude. A warm day in Denver requires a longer takeoff roll than a cold day in Boston.
A little be more complicated than that - you have to consider the wing design, camber, etc. I'm Showing the P-39 had a NACA 0015 wing at the root, a NACA 23009 at the tip, someone like Bill or GregP could probably do the math and tell you how that wing will perform in thinner airWith a bit smaller wings, P-39 may not be as stable as some other types in the (effectively) thinner / hot air?
Living and flying around the Denver metro area, I could attest to that. The airport where I fly out of is about 5600' MSL, I've seen days when the density altitude was close to 10,000'I get that, my observation was, maybe aircraft with a little bit higher wing-loading and a shorter wingspan might have a bit more trouble in thinner air. Not saying that's it so, just speculating.
It's calculated. You start with the chart previously posted and then you use performance charts specific to the aircraftIs there an instrument on the aircraft to measure that or do calculate it based on temperature, humidity and barometric pressure using a tool like you linked upthread?
Instruments on airplanes are funny things. In pilot training we had to do a TOLD (Take Off and Landing Data) problem every flight in the T-38 to figure out all your speeds (max abort, se t/o) plus some others I've no doubt dumped from memory. However, while sitting on the ramp at Roswell (home of the little green men and a instrument approach called the widow maker) my IP told me to dial 2992 into the altimeter (kollsman window) and it will show you what altitude the aircraft "thinks" it's at or, more accurately the pressure altitude of the airfield. Get the temp, do your TOLD, go fly. It's also useful if you think the ATIS (Airport Terminal Information Service) is inaccurate (usually updated once an hour unless conditions change enough). The altimeter can tell you more than just your altitude. In the OV-10 we had a thermometer that stuck out of the canopy, and we would do our TOLD problem just prior to take off. Not sure why, we took off below engine out take off speed(V2) (plane didn't have enough power to get to V2 on the ground), and in the event of an engine out missed it probably didn't have enough power to go around. If you touched down you would not get airborne again on one engine. That airplane (OV-10A) was a performance dud.Is there an instrument on the aircraft to measure that or do calculate it based on temperature, humidity and barometric pressure using a tool like you linked upthread?
EVERY aircraft does better in cold, assuming not too cold. Cold dry air is best for performance, no matter what aircraft you are flyingwhy some types did better in tropical environments and some in cold.
EVERY aircraft does better in cold, assuming not too cold. Cold dry air is best for performance, no matter what aircraft you are flying
In theory (effectively) thinner air at lower altitude might make for higher speeds but a lot of WW2 aircraft seemed to have problems with cooling in high temperature environments.
Spitfires were extensively tested by the RAE in regards to the who what and when and their effects speed, aerials, guns, blisters, ejection ports, rear view mirrors, exhaust types, panel fit and over paint condition and fit and finish where all tested and they had no trouble getting a 20-30mph increase in speed from Mk1's through to MkIX's by incorporating all the above.The RAF and Supermarine conducted tests for all sorts of reasons, like producing a Spitfire with all flush rivets, covering them with split peas and progressively removing them to see how speed was affected.