L-39 sim nits

[jonboede]

Just a few things I've noticed that don't feel right to me in the Albatros:

 

1. L-39s are never left on the ramp with the flaps down and gear doors open. The only time I have seen this is with L-39s that have been sitting out to rot for years on Kharkov air base in the early 2000s (probably so that they can be inspected to make sure no small creatures were making a home in the gear wells -- but even then, flaps were in the up position). The doors are latched and will not "bleed down" over time, even with zero hydraulic pressure in the main and emergency systems. In operational situations the aircraft are always doors closed, flaps up. In order to get the gear doors open when the gear are down, you have to pull the emergency gear lever (when pressure is still in the system), which you will see is not a procedure in the checklist. I checked with my friend who was in charge of the East German L-39s and he said no, never are gear doors left in this condition. Also, flaps in the up position. Leave the flaps down after parking and guess who's buying the beer?

 

2. When sealing the canopy there there is a slight hissing sound as you go through the middle of sliding the seal/air-conditioning lever. Over about 5 seconds the outside noise is gradually reduced as the canopy seals come to full inflation. The current sound level in the cockpit sounds like an unsealed canopy. I would say the sound gets cut by at least 1/3, almost 1/2 of the current noise level after the canopy seals. The L-39 is a very quiet aircraft. When the person in the rear seat records a flight with a handheld camera, you can almost make out their normal conversations on the video. If they're shouting something like "oh sh!t!" it's perfectly clear over the engine noise. It takes a long time for the air conditioning valve to open, so there's a sequence of hissing, then noise reduction, then the conditioner emergency C&W light going off that has a certain "feel" to it. In the sim, you just move the lever and wait a long time... in the real plane there are these other things going on and so it feels like it takes less time even though it still takes forever for the a/c bleed valve to open.

 

3. When the flaps finish moving into the selected position, there is a very positive, satisfying GLUNK noise that comes from deep within the aircraft body. This is the sound of the electrohydraulic valve closing to discontinue flow of the hydraulic fluid to the flap actuators. This is most noticeable at low RPMs of idle or during taxi. The combination of the GLUNK at the same time the selector switch pops back to your finger provides very nice feedback that the aircraft is in the configuration you asked for.

 

4. One of the things that would be nice is: instead of hitting RALT+HOME to put the throttle in the idle position, sliding the throttle up and back would put it in the idle position. In the real airplane the recommended procedure is to quickly and smoothly move the throttle from stop to nearly all the way forward and then back to the idle position (where the lockout prevents it from being moved to the stop position). There is some slop in the throttle linkages and coming back to idle instead of going forward to idle apparently is the better way to do it. Jan Vlček's son, Václav told me this and he was an "engine guy" at the Aero factory, so I take it as gospel. Plus, I'd rather move the throttle than some key combination.

 

5. I don't know about all the failure modes that are modeled in the sim, but one that is common is that the "music box" that sequences the start looks for oil pressure in the safir at 30 seconds after the turbo button is pushed. If it doesn't get the oil pressure (because a small filter likes to get clogged), it cuts the starter. If a pilot doesn't wait until after the 30 second mark in the start to push the main engine button there is a danger of fuel and spark being introduced to the engine just at the time the air starter is dropping out. Can be very bad. This is one of the many reasons the stopwatch should be clicked for both the turbo and the main engine start.

 

6. My only other observation is that "momentum" doesn't seem to be modeled too well in any of the aircraft in the sim. The L-39 flies right at all the numbers but doesn't "feel" like a 10,000lb aircraft. In the real aircraft you can grab the stick and "stir the pot" by making a circle 9" in diameter in a 1/2 second and the airplane doesn't move much, it just wobbles slightly. In the sim, aircraft are properly responsive, but they don't feel like they have "weight" to me.

 

Otherwise, this is an almost perfectly modeled L-39 sim. Feels and looks like starting and flying the real thing!

[gospadin]

Just a few things I've noticed that don't feel right to me in the Albatros:

 

...

 

4. One of the things that would be nice is: instead of hitting RALT+HOME to put the throttle in the idle position, sliding the throttle up and back would put it in the idle position. In the real airplane the recommended procedure is to quickly and smoothly move the throttle from stop to nearly all the way forward and then back to the idle position (where the lockout prevents it from being moved to the stop position). There is some slop in the throttle linkages and coming back to idle instead of going forward to idle apparently is the better way to do it. Jan Vlček's son, Václav told me this and he was an "engine guy" at the Aero factory, so I take it as gospel. Plus, I'd rather move the throttle than some key combination.

 

...

 

Otherwise, this is an almost perfectly modeled L-39 sim. Feels and looks like starting and flying the real thing!

 

#4 is something that Razbam definitely got right on the Mirage. Moving to idle detent from stop is done exactly as you describe above.

 

I personally bound my warthog idle detent to match, but I agree, something like the above would be nice.

[dotChuckles]

Sounds like you operate one of these in real life. I love hearing this kind of detail. Hope we can see it in the sim! :thumbup:

[grunf]

Hope the ED will implement your suggestions into the sim. :thumbup:

[Koriel]

 

6. My only other observation is that "momentum" doesn't seem to be modeled too well in any of the aircraft in the sim. The L-39 flies right at all the numbers but doesn't "feel" like a 10,000lb aircraft. In the real aircraft you can grab the stick and "stir the pot" by making a circle 9" in diameter in a 1/2 second and the airplane doesn't move much, it just wobbles slightly. In the sim, aircraft are properly responsive, but they don't feel like they have "weight" to me.

 

I am in full agreement with you on this one!

Edited December 31, 2015 by Koriel

[Yo-Yo]

I am in full agreement with you on this one!

 

Did you scale joystick movement to the real stick.full travel?

[Koriel]

Did you scale joystick movement to the real stick.full travel?

 

I was responding to his general statement regarding momentum and inertia in all DCS planes. I think it's been improved over the years but still doesn't feel right somehow. I'll have to think and fly a bit to see if I can come up with a good example of what I mean. For now I can say that for some planes it feels like they are rotating around their COG and any quick, and large flight control input and subsequent release makes the plane "snap" back towards it's original attitude like there's no inertia and momentum to overcome.

 

And to answer your question, No. I don't adjust any axis on my X52 Pro.

[OnlyforDCS]

Did you scale joystick movement to the real stick.full travel?

 

This is a great point. A lot of times we forget that our own joysticks have much shorter throw and as such very fine movement of our joysticks can translate to relatively large movements of the control surfaces.

[Koriel]

This is a great point. A lot of times we forget that our own joysticks have much shorter throw and as such very fine movement of our joysticks can translate to relatively large movements of the control surfaces.

 

Stick travel is completely different for different airplanes. I see in the pit that the Mirage stick actually has quite a small range. The F16 stick is quite a bit less even.. ;-). But when you see a cockpit video of the MiG29 that you'll see quite a bit more travel being possible.

 

On planes that I have flown it sometimes suprises you what the same deflection of a stick does to a plane. Some older planes you could really throw the stick all around and just experience a wobble. This goes for gliders, single engine planes, multi-engine turboprop and jet aircraft. Generally on newer planes the effect when moving the controls is quite a bit more pronounced. And don't forget the effect speed has on control feel and responses. On smaller planes without any compensation it can double the force required for the same stick travel.

[OnlyforDCS]

Stick travel is completely different for different airplanes. I see in the pit that the Mirage stick actually has quite a small range. The F16 stick is quite a bit less even.. ;-). But when you see a cockpit video of the MiG29 that you'll see quite a bit more travel being possible.

 

On planes that I have flown it sometimes suprises you what the same deflection of a stick does to a plane. Some older planes you could really throw the stick all around and just experience a wobble. This goes for gliders, single engine planes, multi-engine turboprop and jet aircraft. Generally on newer planes the effect when moving the controls is quite a bit more pronounced. And don't forget the effect speed has on control feel and responses. On smaller planes without any compensation it can double the force required for the same stick travel.

 

Yeah, I totally get what you are referring to, I just never had a problem with it in with the L39 in this sim. The force feedback in this module is done perfectly, and I never look at what my stick is doing really since I can feel the response through the joystick. As the plane slows down you really do need more throw, and conversely as it speeds up much less movement is required. I think I would have a much harder time with a regular joystick, in fact I can't recommend the MS FFB2 stick enough! Everyone should have one in their home ;)

[msalama]

to relatively large movements of the control surfaces.

 

Exactly. And the answer is curves applied sensibly.

[Yo-Yo]

The declared issue with inertia has its origin not in the FM. Of course, I mean only DCS planes I am in charge of. Moments of inertia, control effectiveness are known for the most of our planes, or, in the case of lack of date, the unknown values can be calculated with high accuracy - 5...15%. The reason is a difference in perception in a real plane with real controls and accelerations.

[SilentEagle]

The declared issue with inertia has its origin not in the FM. Of course, I mean only DCS planes I am in charge of. Moments of inertia, control effectiveness are known for the most of our planes, or, in the case of lack of date, the unknown values can be calculated with high accuracy - 5...15%. The reason is a difference in perception in a real plane with real controls and accelerations.

 

I will have to agree here. My L-39 EFM suffers the same "over-responsiveness" as many other recent additions to the DCS module aircraft list. Joystick curves are the simmer's solution to this lack of feedback. However, aircraft with FBW flight control systems are a little more well behaved to a human's inputs on a simulation and responses are more in line with what seems correct. Even in those cases, however, most FBW aircraft have some artificial control feedback forces to give the pilot's resistance to requested inputs.

[jonboede]

Cockpit noise... at 0:15 you can hear me say something even though I'm in the front and the camera is in the back. Also, conversations in the last 30 seconds.

 

https://www.facebook.com/jon.boede/videos/vb.1167655370/10203697574537700/?type=3

Edited January 3, 2016 by jonboede

[ShadowFrost]

I would like to point out something... Many L-39s at Oshkosh and other airshows tend to leave their flaps down when locked up. Whether this should or should not be done I see it in at least 3/5 L-39s that are parked. I would mention something about the position of the gear doors but cannot recall if they were open or closed.