True Altitude?

[Soldier_Fortune]

Hi again FrankB.

I was reviewing the equations, and it seems the Air density calculation is wrong.

It's rare, because they are the ISA (International Standard Atmosphere) ones. But it would be possible.

The formula I've posted has given you a TAS = 367 km/h, right?
I've calculated TAS = 340 km/h with an E6-B, and I confirmed this result with an app for Android which I have.

It would explain why your bombs fall short: calculated TAS is greater than the real, and therefore the calculated drop angle also is greater by about 2 or 3º. Finally this angle causes that you drop your bombs too soon, missing the target.

Please, use the following equations:

- Pressure at bombing altitude:

P = 101325*[(Tmap-0.0065*ALT) / Tmap]^5.25

- Air density at bombing altitude:

AD = 0.0036*[P/(Tmap-0.0065*ALT)]

The temperatures must be converted into Kelvin before they're used in the equations above (T+273).
The pressures are given in Pa (Pascals).

These equations are also from ISA and I've checked them right now.

For your data:

Tmap = -17 ºC = 256 K
T @ 2000 MSL = -30 ºC = 243 K
Po = 101325 Pa
P = 77071 Pa
AD = 1.142 kg/m3
AD_std = 1.225 kg/m3

Then:

TAS = IAS * SQRT(AD_std/AD) = 330 * SQRT(1.225/1.142) = 342 km/h

With this TAS your drop angle should be right.

Please: test these equations, and let me know how they work for you.