Altimiter setting in a F-15i Israeli Theater
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Presently, I am flying in the ITO with an F-15 squadron. I have a question about setting the QNH setting and having no way to set the altimeter in this aircraft. I am wondering if anyone knows the key settings for increasing and lowering the altimeter setting. I searched through the controller settings in the setup. I was not able to find anything useful. I would appreciate this, mostly because it really helps on foul weather approaches and landings.
Thanks to all.
Raven
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If it helps, you can always figure out the effective height if you know the QFE - or if you know QNH and the field elevation.
A pressure altimeter measures ISA height above the set datum. If you cant adjust the altimeter setting in the aircraft, and it remains on 1013 hPa, then it displays pressure altitude - height above the 1013 hPa pressure level, in feet.
If the QFE setting given by tower is 1030, for example, you know the altimeter will read negative 810 ft at touchdown - as air pressure decreases by 1 hPa per 30 ft (roughly enough for this purpose, anyway).
If tower gives QFE as 1000, that is 13 hPa less than ISA, 13 times 30 is 390 ft, so the altimeter will read 390ft at touchdown. This is because the air pressure at touchdown will be 1000 hPa, and the altimeter is reading height above the 1013 hPa pressure level, which is 390 ft lower than ground level.
If you only have QNH and field elevation, then you can add another step in the process to find the height required, as above. If QNH is 990 hPa, field elevation is 250ft, altimeter is stuck on 1013 on the subscale and wont move…
the altimeter is measuring height above the 1013 layer, but the SL pressure is only 990 hPa. That is 23 hPa less, so at SL the altimeter will read 23 * 30ft = 690ft.
The field is even higher, and pressure there will be even lower. The field is at 250ft above sea level, which we can just add to the SL pressure height: 940ft.
Now we know the pressure height of the field, 940 ft. We can even figure out QFE here if we wanted to - but if the goal is to use pressure height for the altimeter, then finding QFE isnt much use to us.
Still! If the field is at 940ft above 1013 hPa, and pressure decreases by 1 hPa per 30 ft… then we can calculate the QFE pretty simply! 940/30 is close to 93/3, which is 31 - so 940/30 is 31 and a third. Call it 31, and we know the QFE must be 31 hPa less than 1013 - which would make it 982 hPa.
If you got through all that, then I guess Ive got the callback for you to add to your keyboard commands, if you like. The callbacks are SimAltPressDecBy1 and SimAltPressIncBy1 to increase or decrease the altimeter setting by 1 hPa.
You would have to add those to your keyfile, and assign a command to them. I think they are actually mapped by default, but not sure what to. I dont recognise 0xC8 as a XT scancode (which seems to be its default mapping) - but then its not my area of expertise.