Why AJS-37 flying 1.32M above the ground in level flight?

[Lynnux]

On 10/31/2020 at 5:28 AM, rossmum said:

so maybe the overall drag modelling needs some adjusting.

That's for sure. There are aircraft with contradictions like the Viggen where you cannot tell if this possible but your gutfeeling already tells you that something is wrong.

Flying 1600 kph all time but not having enough thrust to fly level with some ordnance and gear down on 100% military is such a contradiction. On some Persian Gulf maps I couldn't even keep the speed at low level and 100% military with gear up and the same loadout. You need to climb to like 1000+m to be able to fly on just military. Don't know if that's realistic.

Ah yes, I forgot the Viggen was never build for low level flight, sorry

[renhanxue]

4 hours ago, m4ti140 said:

Apparently the engine is underperforming, which seems to have evaded testing due to drag issues. As you climb the ridiculous overperformance transforms into significant _under_performance. The aircraft should break Mach 2 in clean config higher up (like 7-8 km), but it doesn't, and from what I've seen it can't do that even after triggering the aforementioned negative drag bug. A review is long overdue.

 

Why do you think it should be breaking Mach 2? The flight manual certainly doesn't say or even imply it is capable of doing that. At ISA -15° it may be capable of touching the Mach 2 line (or at least it's theoretically capable of sustaining that speed in level flight) but I'm not sure you could get it to accelerate to 2.0 in reality without running out of fuel. It doesn't have variable geometry intakes so it really has no business above Mach 2.

 

I believe it is underpowered in DCS on mil power, though.

Edited June 6, 2021 by renhanxue

[Lynnux]

On 6/6/2021 at 6:17 PM, m4ti140 said:

Apparently the engine is underperforming, which seems to have evaded testing due to drag issues. As you climb the ridiculous overperformance transforms into significant _under_performance.

The behaviour being totally underpowered on Persian Gulf maps was a bug which is gone. One symptom was the engine RPM going up and down on idle throttle. That's not happening anymore, now engine control only oscillates a bit when you throttle up or down.

[Sideburns]

Anyone retested since the patch given "Updates to sidewinder pylon drag coefficients."?

 

I did a quick test (standard ME parameters for Caucasus, 10-20m above sea level):

 

1580kph for a Viggen spawned in without weapons

1450kph for x-tank and rb24j/rb74

1540kph for x-tank jettison but retaining rb24j/rb74

1710kph for an x-tank and rb24j/74 fire off, pylon retain

1630kph for an x-tank and rb24j/74 fire off and pylon jettison

 

Still too quick it seems, odd behaviour with the pylon jettison slowing the jet down.

[rossmum]

Yeah, retested it and threw some tracks in the other thread. Got to 1700 with all 6 missiles fired and tank jettisoned, when I jettisoned the rails it rapidly decelerated.