Trigger Waypoint: TAS or IAS?

[Charon]

Does the speed parameter of the waypoint trigger control the AI's TAS or IAS? Thus, should I increase these values for high altitude flights?

 

ANSWERED: IAS, see below.

Edited April 27, 2023 by I./JG3_Charon

[IckyATLAS]

This remains a mystery to me.

[Charon]

I suppose this is easy enough for me to test:

 

This test was conducted at 6000m and standard atmospheric conditions. I had an AI bf 109 G-2 fly to a waypoint while pacing them in another G-2, also under AI control with the formation command. (I assume a single plane that I give over to AI control would have the same result, but I wanted to rule out the possibility of full-time AI and player-delegated AI behaving differently). OAT at 6000m was -25C, measured in the He 111H-6.

 

test IAS (actual)   alt     TAS (actual)   nominal
a    391            5950    535            400
b    468            5950    630            500
c    252            5900    345            50

 

So the actual TAS achieved is in fact much higher than nominal waypoint speed, and I conclude the AI targets the IAS of the waypoint (or perhaps something a little below the nominal speed, to hedge against mission designers setting too optimistic targets), not the TAS. Note also that the AI will not stall the plane, even if the selected IAS is too low.

Edited April 27, 2023 by I./JG3_Charon

[Jaegermeister]

I also did a simple test, but from a slightly different approach.

 

Flight #1, 500 meters altitude, 130 kph set airspeed on waypoint, 0 m/s headwind

 

 

Flight #2, 3000 meters altitude, 130 kph set airspeed on waypoint, 0 m/s headwind

 

Flight #1, 500 meters altitude, 130 kph set airspeed on waypoint, 3 m/s headwind

 

 

The anemometer can only calculate indicated airspeed.

 

A 3 meters per second headwind should add approximately 11 kph to the indicated airspeed on the Anemometer, but appears to have no effect on the relationship of the HUD airspeed to the indicated airspeed. Since the RPM stayed constant at 1300 rpm through all 3 tests, this is odd.

Based on what I see, it appears that the waypoints are attempting to maintain the targeted ground speed, adjusted for 500 meters altitude. Your indicated airspeed will then vary according to your altitude, which is what I have seen in game with bomber formations flying at different speeds with the same settings at slightly different altitudes,

 

Since the airspeed indicated on the HUD does not change relative to the altitude, but indicated airspeed should be progressively lower than groundspeed at higher altitude, not higher, and windspeed should have an effect on one of them, I can only conclude that the waypoint target speed is linked to the HUD airspeed which is displaying calculated ground speed, not true airspeed and the indicated airspeed is incorrectly calculated.

 

If others agree, I will ask in the tester forum and see if it needs to be addressed. 

 

Edited April 27, 2023 by Jaegermeister

[Charon]

@Jaegermeister, the anemometers actually display something close to TAS. See this post:

 

 

[IckyATLAS]

Even if I do not have a definitive point and did not test, I always went by the following rule of thumb:

 

If you fly the plane, then what you see in your plane is IAS. The only thing that is not clear for me is if there is an influence from windspeed (up or downwind).

 

When you set a speed for IA then it is the Ground Speed as long as the speed is compatible with the plane capability, considering the slope between two waypoints, not considering the atmospheric conditions. The slope is important because it depends on the climbing ability of the plane. And in general it is there that you have problems with heavily loaded bombers. If the slope is too steep then you get problems in terms of effective altitude reached and final speed at waypoint for those bombers. And when you have climbing turns with a too short radius it becomes even more difficult to set it right.

 

Typical is a Pe-2 with maximum load. The JU52 and C47 can also be tricky. It is impossible to land an IA  C47 on the Gelendzhik-1 airfield (Kuban map) from the north-east. It will 90% of the time crash in the mountain, and I did really test a lot to make it work, alas! But in reality the plane can very well do it. It is just the landing pattern and landing IA procedure that does fail with this plane.

 

 

Edited April 28, 2023 by IckyATLAS

[FeuerFliegen]

Winds would only affect your airspeed if you are sitting on the ground.  They would affect your ground speed though.

Edited April 29, 2023 by SCG_FeuerFliegen

[IckyATLAS]

On 4/29/2023 at 4:02 PM, SCG_FeuerFliegen said:

Winds would only affect your airspeed if you are sitting on the ground.  They would affect your ground speed though.

Yes sure, I wanted to mention that as you see only the IAS if you are headwind or downwind is really your groundspeed different, which you cannot tell with the onboard instrument. How is groundspeed impacted I have not tested.