Questions about real L-39

[JG14_Smil]

Hello,

 

I'd like to learn more about the actual L-39 for my cockpit construction. I was hoping I could post some questions here. Thanks in advance for any answers and anyone is welcome to ask if they need.

 

Regarding over-speed of landing flaps. In DCS, when the flaps auto retract from the landing position, they retract to 'flaps in'. I find this dangerous and I was wondering if the flaps would retract to the take off position instead in real life?

 

Does the L-39 throttle have a damper installed to slow operation?

 

On the ejection handles, I see what appears to be fail-safe paddles on each one(?). I'm guessing to make sure hands are in position for pulling each one properly. I can model this if it is in the actual L-39.

 

that's all for now...

 

thanks for any help.

[Bourrinopathe]

The flaps are automatically retracted to "Flight" position (zero degrees) at airspeed above 310± 15 km/h

That's most probably to avoid structural damages.

Also the flaps deployed in the landing position adds a "nose up" trim deflection, so the pitch attitude difference between the two positions (landing/flight) is somewhat reduced.

 

From what I've read, the throttle is mechanical and pretty simple with no damping.

The flight manual also repeatedly indicates the throttle should be operated with care. It's also supposed to be "responsive".

I can't confirm that though.

Here's a L-39 throttle on EBay. (it looks suspicious)

 

About the ejection handles:

When a decision to eject has been taken, the pilot shall grasp the double firing handles (ejection handles) with both hands, squeeze the unlocking hand-rails and pull them continuously upwards, until the seat is fired out of the cockpit. The rest of the ejecting sequence operation, up to the main chute deployment, is fully automatic.

 

That should answer your question ;) Squeeze both handles (and paddles) and pull until the sequence is triggered.

Edited February 28, 2017 by Bourrinopathe

[Ramsay]

On the ejection handles, I see what appears to be fail-safe paddles on each one(?). I'm guessing to make sure hands are in position for pulling each one properly. I can model this if it is in the actual L-39.

The December 2005 L-39 Technical Newsletter has some ejection handle pictures that might help in it's construction. Unfortunately, I can't find a valid archive link for the pdf but can share the pictures.

 

 

Edit: found a valid link - ftp://sharepoint.jetpro.ca/Outgoing/L39%20Manuals/Aero%20Contact%20Articles/2005%2012.pdf

 

Full archive: ftp://sharepoint.jetpro.ca/Outgoing/L39%20Manuals/Aero%20Contact%20Articles

Edited February 28, 2017 by Ramsay
Add Safety Card

[JG14_Smil]

Thanks for the great answers!

 

I know about the over-speed structural damage issue, but I've had my flaps go back to flight position while I was still in slow flight. That can be a handful when that slow. I may be getting a shorted button press to cause it (in my cockpit). It keeps me on my toes!

 

Excellent info on the throttle. Looks like there might be a friction control lever, when looking at the DCS throttle. On the Ebay throttle, does the red knob handle control friction?

I thought maybe it would have a damper to help with the laggy operation. Does not look hard to build this.

 

Yes, those are what I refer to on the ejection handles. Sort of like Colt .45 palm safeties. I'll build them that way.

 

Thanks so much Ramsey.

 

{backs away from the Ebay listings... that is one slippery slope there!} :)

Edited February 28, 2017 by JG14_Smil

[Ramsay]

Looks like there might be a friction control lever, when looking at the DCS throttle. On the Ebay throttle, does the red knob handle control friction?

 

Page 15 of this data sheet, shows the forward throttle has a "friction pawl" (In the Aero Vodochody Flight Manual it's also called an Arrestment Lever). It's in the same place as the red knob on the ebay throttle but shaped differently. The aft throttle does not have a "friction pawl" fitted.

 

http://www.csobeech.com/files/L39DataSheet.pdf

 

Note: in the May 2003 Aero-Contact Newsletter - there's discussion of the need to check for seized linkage bearings if the throttle is getting 'heavy' and there's no need to use the Arresting Lever anymore. There are pictures of the linkage/bearings but not of the throttle.

 

ftp://sharepoint.jetpro.ca/Outgoing/L39%20Manuals/Aero%20Contact%20Articles/2003%2005.pdf

[JG14_Smil]

Thanks so much for this Ramsey,

 

That safety card was interesting, showing the manual seat separation lever. I was going to use that as a seat height adjustment, but I won't do that now. Any idea of levers to left side of seat would control the seat height servo?

[Ramsay]

Any idea of levers to left side of seat would control the seat height servo?

 

Yeah, there is a switch on the LH side of the ejection seat to adjust 'Bucket Height'.

 

Unfortunately the photo in the 1991, T.O. 1T-L39ZA-1 manual is both confusing and poorly reproduced.

 

 

Source: ftp://sharepoint.jetpro.ca/Outgoing/L39%20Manuals/AFM/L39%20Z%20AFM%20(Scanned).pdf

 

I think this (figure 1-52, item 8 ) from TO 1T-L39C-1 is probably accurate

 

but can't be 100% sure as the diagram (1-54) two pages on, seems to mislabel several of the handles/functions.

 

Source: http://www.anythingaboutaviation.com/wp-content/uploads/2013/01/Aero-L-39-Flight-Manual.pdf

[Gekko312]

Hi,

 

I can answer these questions for you, I've got about 1,000 hours in the real L-39.

 

- If you exceed the flap auto-retract speed they do retract fully, not to takeoff. This isn't a problem unless the airspeed switch has a malfunction, which is not uncommon.

 

- There isn't a damper on the throttle, but the acceleration of the engine is limited by the fuel control. You can move the throttle as fast as you want, and the engine will accelerate or decelerate to get to the selected power as fast as the fuel control allows it to. Part of the first flight of the day runup is to slam the throttle to mil power from idle and time how long it takes to get to 90% of max fuel pressure. It has to be between 9 and 12 seconds.

 

- The paddles on the ejection handles are safeties, but only one has to be pulled to allow the handle to move and initiate ejection. It isn't designed to get you into a good position, but to reduce the possibility of inadvertent ejection.

 

- On the jet the throttle friction is just to the right of the throttle in the front seat. It is a lever that has no friction when full aft, and when pushed forward adds friction to both throttles (as they are mechanically linked).

 

- The lever on the right front of the seat is the Emergency Chute Separation level, which allows a manual bailout or manual man-seat separation after ejection. The lever on the left front of the seat is the shoulder harness release, which allows you to release the shoulder harness lock to move more freely in the cockpit. During an ejection the shoulder harness is retracted with pyrotechnics to pull the pilot back into the seat.

 

Let me know if you have any more questions, the L-39 is a great jet and the DCS one is very close to the real thing!

 

Gekko

Edited March 4, 2017 by Gekko312

[Bourrinopathe]

Fantastic info Gekko312! Thanks a lot for your insight.

I'm sure some of us will have more questions about the L-39!

[JG14_Smil]

Hello to all,

 

I have been tuning the tactile feedback vibrations in my seat and I have been looking for info with no luck as of yet. I was wondering the approximate RPM range of the turbofan engine in the L-39.

[Justin Case]

Thanks for your input Gekkko, this makes me more certain that this is my favourite module. Well done and back to basics!

[Ramsay]

I was wondering the approximate RPM range of the turbofan engine in the L-39.

HP Info from the Russian manual

106.8% = 17600 rpm

103.2% = 17000 rpm

99.6% = 16400 rpm

 

is in rough agreement with an engine manual which lists some percentages/ranges for fuel adjustment screws, etc.

Values from AI-25TL Maintenance Manual		
percent	HP rpm	HP 100% (calculated)
1.50% 	 250	16666
4.80%	 790    16458
5.30%	 875    16509
5.70%	 950	16666
8.75%	1440	16457
47.00%	7750 	16489

[JG14_Smil]

Thanks very much Ramsay. Much higher than I expected.

[kadda]

hello every body, i saw here questio about ejection seat...

 

what i can tell you is that there s two version of ejection seat for the L-39 the most common model is VS-1BRI

the new one is K-96 ( the same model that s used in the YAK-130 ) and in the same time it s a modification of the seat installed in the mig-29 and SU-27 familly ...

 

in the old model by pulling one hand there s a risk that the system will not work properly, in the new model this case don t exist ...

 

and in the new model there is no fail safe paddels, and have a "logical" bloc , to select if there s two pilots or just one , in case of real ejection, if there is only one pilot so no need to eject the second seat than the first ... as i remember in the VS-1BRI in case of ejection the two seats are always ejected the second cockpit then the first and at low altitudes its lsot of time if there s onl one pilot but i need to have a look at the docs to tell all the + changes that bring the K-96...

 

if someone need the performances or more information about minimum altitudes of use just post a question will be happy to help ...

 

about the flaps i saw that the question was already answered they fully auto retract at 310Km/h to avoid dommages in ther contruction , and over that speed even if you push the button they still retracted ...

Edited April 13, 2017 by kadda

[Sydy]

hello every body, i saw here questio about ejection seat...

 

what i can tell you is that there s two version of ejection seat for the L-39 the most common model is VS-1BRI

the new one is K-96 ( the same model that s used in the YAK-130 ) and in the same time it s a modification of the seat installed in the mig-29 and SU-27 familly ...

 

in the old model by pulling one hand there s a risk that the system will not work properly, in the new model this case don t exist ...

 

and in the new model there is no fail safe paddels, and have a "logical" bloc , to select if there s two pilots or just one , in case of real ejection, if there is only one pilot so no need to eject the second seat than the first ... as i remember in the VS-1BRI in case of ejection the two seats are always ejected the second cockpit then the first and at low altitudes its lsot of time if there s onl one pilot but i need to have a look at the docs to tell all the + changes that bring the K-96...

 

if someone need the performances or more information about minimum altitudes of use just post a question will be happy to help ...

 

about the flaps i saw that the question was already answered they fully auto retract at 310Km/h to avoid dommages in ther contruction , and over that speed even if you push the button they still retracted ...

 

 

Hi Kadda,

 

I just would like to say thank you for all the info you provided. Because of that I decided to buy

DCS L-39 today.

 

Thank you!

 

All the best,

 

Sydy

Edited April 14, 2017 by Sydy

[kadda]

Hi Kadda,

 

I just would like to say thank you for all the info you provided. Because of that I decided to buy

DCS L-39 today.

 

Thank you!

 

All the best,

 

Sydy

 

:thumbup:

[BSS_Sniper]

We have a member who owns a L39 and is, obviously, type rated in it. He would probably be a better source than most here. I'll give him a link to this post.

[JG14_Smil]

OK, let's talk about aileron trim.

 

In DCS, it is very coarse and I consider it unusable. I have my best luck with a deadband of 1 and nudging the freeplay in my stick, which actually works pretty well.

 

Is DCS aileron trim too coarse in adjustment, compared to RL L-39?

[kadda]

As i know it s very fluid cuz it s linked to a small electric motor, at small speeds 300-500km/h you need to hold the trigger a moment in order to have an effect ... But in real plane it s done naturaly ciz you feel the force on the stick changing ...

 

Envoyé de mon X5max en utilisant Tapatalk

[Pineapple Pete]

Hello Again! I have not had time to read all of the posts but I believe that you can purchase an actual L-39 AFM from http://www.jetwarbird.com

They offer war bird type ratings out of Santa Fe, NM.

by the way, I sent you a quick message in Facebook messenger.

Best.

[JG14_Smil]

Thanks Pete, I'll look into my FB settings. Might be getting blocked.

[humptydumpty]

@smil

 

Great, would love to see the whole pit once done . I just started flying the 39 and she is a beauty , Mig21 was the goto aircraft but I am not going to indulge in combat so L-39 is goto for me now

[Morpheus]

Last week end me and my team were present to a real airshow in France and we met real pilots of L-39 who fly with it in aerobatic patrol. I asked them a question about airbrakes. In DCS airbrakes are not really effective and not easy to use in closed patrol. In real life they are effective and wingman use them to stay near leader, pilot doesn't use throttle because the plane is not powerful. I you decrease power, you loose contact with leader and it's hard to come back in position. It would be cool ED changes this to as real life don't you think ? :music_whistling:

[probad]

fixes are always cool but you need something more concrete than "is effective"

 

you can't discount the possibility that what you consider not effective is considered by the pilot to be effective.

[kadda]

I know that the airbrakes are very effective in the l39 but i know that that plane have a very big inertia, and flying in a patrol with it need a very good sense of anticipation