… so continuing with a discussion we started over at the MSFS forum …
When I look at the flight envelope graph on page 41 of the manual I read it as:
- If the nacelles are at 0 deg … so APLN mode
- I will stall below 105 ktas … unless I raise the nacelles
- … and if I go above 200 ktas … I am required to have them at 0 deg
I interpret the black line as the recommended speed at which I should initiate a nacelles raise … just to have a safety margin far enough from the risk of a stall event.
So at least to me the graph on page 41 does not explain why the AP should not be able to perform VS adjustments below 170 ktas.
Perhaps (in the real world) there is an altitude aspect to this … as the air gets thinner at high altitude any maybe the stall speed goes up dramatically. But there is no diagram in the manual that so far explains such boundaries.
But when I checked that 170 ktas limit I was flying below 3000 ft … so even high altitude would not explain that.
I will check if I can manually fly and trim the Osprey into slow APLN climbs at slow speeds. I am pretty sure that this will work.
So I do consider this 170 ktas speed issue an AP bug.
Miltech Simulations @MiltechSimulationsI can confirm I see the same behavior - around 160-170 ktas, the autopilot does not follow VS. The aircraft stalls between 105-115 (correct as per the graph), depends on your altitude and weight, but flying manually the aircraft has a tendency of pitching down at speeds between 110-140kn ("yellow safety area")
The "black line" on the graph indicates the "Lower Nacelle Indicator Conversion Corridor", and the red areas indicate the absolute lowest and highest airspeed limits during conversion. Conversion must occur within the blue area ("conversion corridor") which depends on the altitude of the aircraft, with the yellow area functioning as a safety margin.
The minimum speed under normal operations is 140ktas, with normal conversion speeds at 160-180 ktas. I would expect that, under normal flight conditions, minimum speed for APLN mode is around 170ktas as this would be the ideal speed for conversion (right in the center of the conversion corridor).
@nenenuiI did some more tests … and I could manually trim (ca 30%) the Osprey into a stable leveled flight at 110 to 120 ktas (and it is pretty windy today in Aden, OYAA).
So I would expect that the AP would be able to achieve a similar outcome.PS: I also was able to reproduce another VS AP bug … but I need some more tests … and I will open a new topic for that … since I think those a distinct issues.
- In reply toMiltechSimulations⬆:@nenenui
I did some more tests and clearly the speed is (actually) not the main issue … that 170 ktas "bug" which I did think I could see must be something else.
Today I had no problem to use the AP in APLN mode at speeds as low as 120 … so yes … the AP can fly as slow as a human could with manual inputs.
So I fully agree that the "bug" which I reported here is "solved", as it did not exist in the first place.
It is something else … and I still can not reproduce it reliably (so far it feels like altitude above ground might play a role … investigating …)