Warbird Information Exchange

Is a "Hot Start" a common occurence in the L-39? Or is this just a one off catastrophe. Any feedback from L-39 drivers would be much appreciated. This happened last weekend at Tamiami Airport in Miami Florida.

That was a "hot start"?

Hot starts are usually immediately recognized by watching the EGT/FTIT on startup, and the engine is shut down. It is a result of there not being enough airflow through the turbines to keep the system regulated. As a result, fuel gets dumped in and ignited, and the temp skyrockets. As soon as the throttle goes to 'off', the ignition in the hot section stops and the 'fire' goes away.

What we're seeing in those photos looks more like an actual engine fire on the ground to me. In fact, it is BEHIND the actual engine hot section where all the damage is.

I'm certainly not an expert on the L-39's engine, but that looks more like a tailpipe fire that got out of hand than a hot start.

The Flight manual for the L-39C states that if EGT rapidly approaches 685 degrees C on start up the engine must be shut down.

Post Toasties Time here................

I was always careful to start to the chopper in a manner that wouldn't cook the engine. Usually my starts were a bit on the cool side, which is better than this happening. I don't know what an L-39 engine costs, but I'd say that this one needs some work........

Sorry to see it happen..

Mark H

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Fly safe or you get to meet me .......

Wow,
I have had a few hot ones, but never doing that much damage.

That looks like a slow turning full fuel start, mostly tailpipe fire, not just a hot start. The back of the engine doesnt look that bad.

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"Hindsight is usually 20% off!"

Could some of you jet practitioner's explain the start procedure of a jet engine? I have no experience and am curious.

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REMEMBER THE SERGEANT PILOTS!

I am in no means an L-39 expert as I work on Bizjets all the time.

In most of the airplanes I work on, the rarity being the Fadec airplanes. You start the engine pretty much the same way. You get it spinning beyond a certain percentage, when you move the power lever out of cutoff to put in the fuel the auto ignition is engaged and it lites off and there is a temp limit you shouldnt exceed. You also make sure there is sufficient oil pressure during the start sequence. If either look abnormal you take the fuel away, and let the engine motor to keep the air moving through it. (the FADEC engines add the fuel in for you, you just hit the start button)
The slower the speed you add the fuel the "hotter" the start.
I was taught to let it spool longer, the more airflow the cooler the start.
I have had a few on their way to the redline, even flames out the tailpipes on a single engine turboprop, but it was pretty obvious that something was not happeneing correctly. (FCU not purged correctly/manual override lever in full throttle position)

I am assuming there was too much fuel or late ignition for that to happen to the Albatross.

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"Hindsight is usually 20% off!"

Here are procedures for the three jets I've flown:

T-37: Push the starter switch to get the engine rotating. At a certain percentage, push the igniter switch until you see a rise in the EGT and the RPM increase. Then, off the igniter switch but keep on the starter switch until a particular RPM after moving the throttles out of cutoff.

T-38: Turn on the huffer air cart until 12% RPM. Press "start" button, then move throttles out of cutoff. Monitor start to ensure RPM and EGT rise at a known relationship.

F-15E: Pull "JFS" handle to start what is essentially a small APU. Raise finger lift on throttle to engage engine. At 20% RPM, push throttle out of cut-off into idle. Monitor start via FTIT and RPM.

In the AS350 ----

Be aware which way the wind is blowing, up the pipe makes for a hotter start.........

Press the starter to spin the engine.

When you hit 12% RPM puss the throttle out of the gate and start moving it forward to induce fuel flow.

Watch the T4 gauge and don't let it hit the $300,000 line (redline)

Advance the throttle slowly watching temp to 35% RPM

At 35% RPM release starter, engine is burning now.........

Advance throttle to 65% ground idle while watching T4.

For flight advance to 100% and lock throttle (it s a helicopter).

On FDAEC models, hit the starter and go for ground idle or flight, computer does the rest..................

Mark H

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Fly safe or you get to meet me .......

I went to a P&WC PT-6 familiarization seminar recently & their openng pic was a still from a video of some homebuilt with a PT-6 with fire from the exhausts to the windshield. It was the engine's first start & the fuel controller had been mis-adjusted. They pointed out the shiny things on the floor, which many folks hadn't noticed yet. They were turbine blades that had been spit out as the engine disintegrated.

Looking at the pics, & not knowing the turn of events, It looks like the damage incurred was from an out of control situation that probably went something like this, 1. a start attempt with a low battery, or for some reason not able to attain the proper N1 speed, 2. a hung start with a failure to accelerate, 3. fuel flow & shutdown was not achieved for some reason, fuel control out of rig, operator error etc. 4. unable to keep enough air coming through th engine to blow the fire out and or no outside help to put out the fire (fire guard). This is not pictures of a "hot start" but rather of an engine FIRE. I hope no one got hurt. Just my 50 cent worth.
Robbie

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Fly Fast Make Noise!

Ahhh,
The famous Wayne Handley and his Turbo Raven first engine start.
The Manual Override lever was saftey wired in the wrong direction.
(The manual override is a Single Engine requirement, in case if FCU issue)
It dumped full fuel in at the start, it cooked the thing. they show that picture at the classes in Montreal too. That was a great airplane to see at airshows until his accident. It was a single PT-6 on a low wing acro airframe. It looked alot like the Turbine Toucan.

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"Hindsight is usually 20% off!"

I went to the same one put on by Covington Engines last week in Raymond, MS. Ron and Fletcher put on a good training event.

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If God had wanted man to fly behind a flat motor, Pratt Whitney would've built one.

Same one. Maybe we bumped into each other & didn't even know it!

I'll put this by Jon and/or Roma unless someone else who knows L-39s really well pipes in, but I'm pretty sure the L-39 engine will auto shutdown in most hot start and "hung start" situations as there are a set of timers that will cause the autostart procedure to discontinue and shutdown the engine. A tailpipe fire due to a incorrectly adjusted fuel injector or a bad igniter looks to be the cause here, and that would not be covered by the automatic systems.

I know the Mi-2 has a 30 second auto-cutout for the start sequence, and I think the L-39's is the same with just a different timing (I think 23 seconds was what I was told...).