L-39 speed?

The L-39 is an absolute jewel and a joy to fly! But I have one question: I struggle to reach a speed of more than 260-270 knots in level flight, as well at low, medium or high altitude. It is only when diving that I can get something like 310 knots or so. (with 50% fuel, no weapons)

This seems to me too slow. One private owner of an L-39 claims on Youtube about 500 mph, which might be exaggerated.

But given the fact that the L-39 is used in A2A adversary roles and as an aerial cinematography platform, I would think you cannot do this with the low top speed of DCS. In DCS, I can definitely do better with a Mustang, Spit or BF-109.

Do you guys also get this low top speed? And do you think it is realistic?

Hello,

Are you trimming the plane? It is very important with the L-39.

Best wishes,

Yes I also suspected trimming so I tried two things:

- trimming to see if I could optimize speed: NO EFFECT

- reset trim since it might have been optimal for take-off, not for level flight: NO EFFECT

If you did not trim, the L-39 would want to go 400 km/hr. Two L-39s trimmed differently will act differently. You can fine tune your speed with the trimmer. I've flown nothing but the L-39 for a year. I see these things...

If you are talking about NTTR, you will get slower speeds due to higher altitudes there. It is realistic. You are almost 2000 feet higher there.

Just just trying to help.

No trouble in the Caucasus with 15°C air temperature and a clean configuration.

+400 IAS @6000 ft with 106% Max throttle, trimmed for level flight (but did have to do a gentle climb/dive roller coaster to get there).

A 4G pull into a half loop and roll, got me to 10,000 ft at 200 kts IAS. I then accelerated to 300 kts before a 20° dive to 2000 ft reaching 430-450 kts IAS.

The L-39C lost it's flaps and half it's ailerons and elevators (AFAIK the speed brake overspeed didn't extend). So it looks like the damage model is still wip.

The L-39ZA didn't suffer the same fate, despite a faster 471 kts IAS exit (AFAIK the speed brake overspeed didn't extend).

Strange that I cannot get these speeds. But I am reassured that for you guys everything seems fine, so I have to check what is going on (on the two different PC's I tested it!)

i also can confirm that reaching speeds over 700km/h are possible, even in level flight. it helps to be low on fuel and enemy fighters are breathing down your neck :)

Thanks Svtony; if the performance matches the real thing than that is fine with me! Indeed the L-39 engine hasn't much thrust.

And I repeat it was just an inquiry out of curiosity, since I absolutely love to fly the DCS L-39. It is an absolute marvel!

Just as a sidenote, is everyone here talking about the same units? The cockpit can be configured with both kmph and kt.

Regards,

MikeMikeJuliet

I always refer to knots. And to be clear: there is no way I can reach 400 knots in level flight with the L-39.

But I understand that this is also the case in real life.

But I understand that this is also the case in real life.

As stated, the aircraft is perfectly capable of reaching 400kts in the sim too. A stupid question perhaps, but are you sure your flaps and gear were up? And what was your gross weight?

Strange, no I'm not flying with airbrakes and/or gear down :) I just struggle to get over 270 knots in level flight.

I fly without payload and about half a tank.

Something must be wrong in my config, I'll try to sort it out.

Do your RPM go to 106% when you push throttle to limit ?

Yes! I can already say that it seems related to the mission files (I always use missions I made and then modify again and again, so some are quite old mission files).

When I just start in a brand new mission in the ME, I now could fly 350 knots level at about 7000 feet, no wind, 60% fuel, no payload. So that is way better as what I have in the missions I was flying.

But anyway there seems a wide consensus her that it is not a genral problem and that I am the only one facing this presumed issue. So I'll dig deeper and when I can pinpoint what it exactly is I'll report back!

Post one of these "slow" mission files then so that we could give it a whirl.

As stated, the aircraft is perfectly capable of reaching 400kts in the sim too. A stupid question perhaps, but are you sure your flaps and gear were up? And what was your gross weight?

Flaps, gear and takeoff/landing lights retract automatically at speeds of 300 kph, 400 kph and 400 kph so this can't be the problem.

@ tflash: I suggest you make a video of your start up procedure, taxi, takeoff and flying around a bit. You might be missing something in the start up procedure or making any mistakes further on.

Only flaps auto retract at 310 Km/h (167 kts) :smilewink:

Flaps, gear and takeoff/landing lights retract automatically at speeds of 300 kph, 400 kph and 400 kph so this can't be the problem.

I know the flaps autoretract, but the gear to my knowledge doesn't. But this can still be a problem, because depending on your throttle usage and trim you often can't even get past the 300KMPH limit if you forget to retract the flaps after takeoff. You just wonder what's wrong with the plane being so ruddy slow ;)

Nothing is wrong with the plane.

I know nothing is wrong with the plane. Read my comment above again.

EDIT: to clarify - if you forget to raise the flaps, trim for cruise and throttle accordingly, you won't get past the 300KMPH limit and your flaps won't autoretract.

Trim has nothing to do with the speed.

Sure it has, together with everything else. Look at the whole.

It wouldn't make any sense if the speed would (noticable) change with the trim setting.

Throttle down, trim consequently up in order to stay level. Sure as hell your airspeed goes down. As I said, look at the whole.

And I'm done here, since I'm not even remotely sure if any of this serves any useful purpose whatsoever. Toodle-yah!

:doh: And where exactly did I claim that the trim tab itself causes any significant drag?

Look, this is what I said:

1) Leave flaps on TO.

2) Apply cruise power, trim for level flight.

3) The L-39ZA doesn't exceed 300KMPH and the flaps don't autoretract.

Or this at least happened the last time I forgot to raise my flaps after taking off. And THAT was all I claimed, NOT anything about the ruddy trim tab. Comprendo?

EDIT: although it has to be said that it's been a while since this happened, I was still running v1.5 instead of NTTR so no idea if the machine still behaves that way.

Which units are you seeing in the cockpit?

https://forums.eagle.ru/attachment.php?attachmentid=148995&stc=1&d=1475018098

If you're seeing the bottom, I think you're seeing your speed in knots and not km...which would explain, maybe?

I always refer to knots! As said I struggled, when flying level, to go faster than about 270-290 knots (of course even the slightest dive increases speed substantially). I did some further testing and it seems related to my X-55 stick & rudder settings on one of my PC's. When I fly the same test mission (just flying level essentially) on another PC with a CH stick, I on average reached about 30 knots more!!!

I'm trying to figure out what causes this for my X-55 stick.