01 May 2025, 06:12 [ UTC - 5; DST ]
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Post subject: Re: L-39 Operators? Posted: 27 Nov 2024, 16:48 |
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Joined: 05/02/15 Posts: 967 Post Likes: +685 Location: Austin, Texas and Argentina
Aircraft: L-39 Albatros
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Username Protected wrote: any L39 operators have issues with the shimmy damper?
looks fairly simple, just larger than a GA one. mine shows no hyd leak; but it obviously needs servicing. I haven't had a problem... make sure the nose strut nitrogen pressure is correct - 370 psi, although Vlad told me some aircraft can be as low as 280 psi. (It may be different for a -ZA model). You may have to jack the nose up to set this correctly. Bruce will know. There should be about 3 fingers-width of strut "silver" part showing. It is very important that nose strut is not over serviced, because it will activate the WOW switch and release brake pressure (brakes will be INOP).
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Post subject: Re: L-39 Operators? Posted: 10 Dec 2024, 14:07 |
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Joined: 05/02/15 Posts: 967 Post Likes: +685 Location: Austin, Texas and Argentina
Aircraft: L-39 Albatros
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Username Protected wrote: For those of you with APs in the L39, do you have Garmin GFC500 ?
Are those servos be powerful enough for the L39? I had the GFC500 installed this summer, replacing an STEC-50. My understanding is you should use torque enhancers for the L-39. (I know this is the case for the pitch servo, I'm not sure if it's also the case for the roll servo). I've been very happy with the autopilot, especially once I adjusted some of the gain settings. I started a thread here as I was trying to tweak the various gain settings: viewtopic.php?f=21&t=230777
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Post subject: Re: L-39 Operators? Posted: 13 Dec 2024, 18:06 |
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Joined: 07/13/19 Posts: 579 Post Likes: +702 Company: USAF and Polaris Program Location: FL
Aircraft: F-35A A-JET L39 A36
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We have them in the Alpha Jets and the GFC500 gets into some light oscillation (+/-100) around .75-85. We put on in one of the L39s but I haven't used it yet, from what I've heard it works well.
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Post subject: Re: L-39 Operators? Posted: 13 Dec 2024, 19:40 |
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Joined: 05/02/15 Posts: 967 Post Likes: +685 Location: Austin, Texas and Argentina
Aircraft: L-39 Albatros
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Username Protected wrote: We have them in the Alpha Jets and the GFC500 gets into some light oscillation (+/-100) around .75-85. We put on in one of the L39s but I haven't used it yet, from what I've heard it works well. Can you clarify what kind of oscillation? Is it altitude +/- 100 feet? I wonder if this could be corrected with the pitch airspeed gain schedule (which isn't documented by Garmin but was recently discussed in my GFC500 thread). Of course this should only be done after the normal gain setup procedure.
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Post subject: Re: L-39 Operators? Posted: 14 Dec 2024, 19:09 |
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Joined: 07/13/19 Posts: 579 Post Likes: +702 Company: USAF and Polaris Program Location: FL
Aircraft: F-35A A-JET L39 A36
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Username Protected wrote: We have them in the Alpha Jets and the GFC500 gets into some light oscillation (+/-100) around .75-85. We put on in one of the L39s but I haven't used it yet, from what I've heard it works well. Can you clarify what kind of oscillation? Is it altitude +/- 100 feet? I wonder if this could be corrected with the pitch airspeed gain schedule (which isn't documented by Garmin but was recently discussed in my GFC500 thread). Of course this should only be done after the normal gain setup procedure.
Yes, approximately +/- 100' which seems to vary with mach. The Alpha Jet has hydraulic flight controls and a system called ARTHUR that does pitch compensation with speed. Additionally, the trim is connected through the ARTHUR to a spring box for "feel." So, between all of that, it may just be hard to adjust to a gain schedule.
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Post subject: Re: L-39 Operators? Posted: 03 Feb 2025, 10:35 |
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Joined: 09/05/09 Posts: 4322 Post Likes: +3108 Location: Raleigh, NC
Aircraft: L-39
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Username Protected wrote: For those of you with APs in the L39, do you have Garmin GFC500 ?
Are those servos be powerful enough for the L39? I had the GFC500 installed this summer, replacing an STEC-50. My understanding is you should use torque enhancers for the L-39. (I know this is the case for the pitch servo, I'm not sure if it's also the case for the roll servo). I've been very happy with the autopilot, especially once I adjusted some of the gain settings. I started a thread here as I was trying to tweak the various gain settings: viewtopic.php?f=21&t=230777
slowly, incrementally adding the AP parts. my choices were 1) behind the throttle, or 2) in the hole for the glove-box. i hate losing the storage box, but i wanted to AP a little more forward. happy so far-- and i can easily move that panel and replace the glovebox if i ever want to change it...
Please login or Register for a free account via the link in the red bar above to download files.
_________________ "Find worthy causes in your life."
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Post subject: Re: L-39 Operators? Posted: 03 Feb 2025, 12:10 |
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Joined: 05/02/15 Posts: 967 Post Likes: +685 Location: Austin, Texas and Argentina
Aircraft: L-39 Albatros
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Username Protected wrote: slowly, incrementally adding the AP parts. my choices were 1) behind the throttle, or 2) in the hole for the glove-box. i hate losing the storage box, but i wanted to AP a little more forward. happy so far-- and i can easily move that panel and replace the glovebox if i ever want to change it... I think your choice is the best given your constraints. That's about where I have mine. I think yours is further forward which is probably easier to use. Now you can set the heading and altitude bugs using the autopilot knobs instead of the G5 knobs.
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Post subject: Re: L-39 Operators? Posted: 03 Feb 2025, 12:59 |
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Joined: 12/03/14 Posts: 19922 Post Likes: +25000 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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L-39 guys: Can any of you identify the team in this photo? Attachment: l39-doubletake.png They performed at Sun-n-Fun recently. Mike C.
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_________________ Email mikec (at) ciholas.com
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Post subject: Re: L-39 Operators? Posted: 10 Mar 2025, 10:20 |
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Joined: 12/10/07 Posts: 34611 Post Likes: +13243 Location: Minneapolis, MN (KFCM)
Aircraft: 1970 Baron B55
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Username Protected wrote: Finally got “dash 3” in the jet. I made her wait until she was physically strong enough for egress. She might be the one who makes it a career… I think that grin in the second picture says it all!
_________________ -lance
It's easier to fool people than to convince them that they have been fooled.
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Post subject: Re: L-39 Operators? Posted: Yesterday, 12:02 |
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Joined: 09/05/09 Posts: 4322 Post Likes: +3108 Location: Raleigh, NC
Aircraft: L-39
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Sunday I had an anti-skid failure in the L39, and blew a main tire on landing (that's a whole other story).
While changing the tire (on the runway no less), I needed a tool I didn't have, and have not seen, so I welded one together.
This allows you to compress the wheel halves, to get the bolts through, with the new tire. Otherwise, the elasticity of the new tire prevents the wheel-halves from coming close enough together to get the nuts onto the wheel-bolt threads. Impossible to do by hand (with a guy standing on the tire...)
cost me about $5 to make. also works on the nose-gear.
12" carriage bolt from lowes, with nut, 2" x 1/4" square tubing split, 5" long. Wood blocks will allow it to work on smaller wheels.
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_________________ "Find worthy causes in your life."
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