Warbird Information Exchange

T-33 hydraulic system is small (1 gal fluid, 1000 psi) so you can only actuate one high-load component (speedbrakes or landing gear) at a time. Extending speedbrakes temporarily drops normal hydraulic system pressure (800-1200 psi) to approx 500 psi where the accumulator catches it from bottoming out to 0 psi. Since the race pilot in the "almost accident" you cite extended then immediately retracted speedbrakes, the hyd system was overwhelmed and went to 0 psi (I've done this several times in my T-33), eliminating his aileron hyd boost temporarily even though aileron inputs don't put a big load on hyd system pressure. Once actuating a high load hyd component, the pilot has to wait at least a few seconds (longer if actuating landing gear) for system pressure to recover before actuating another high load hyd component. The point isn't to slam him but to point out the fact the anxious moment wasn't caused by the fact that it's a jet and they're simply too dangerous to race. I talked to the pilot in question about this very issue. I'd be curious to hear what the flight safety guys have to say about the future of jet races vis a vis the L-39 accident. The solution may as simple as increasing/tuning the pilot training and evaluation process at PRS or setting up a wider course for them. If they do race next year, I'd like to see it first-hand so I can better see what y'all are talking about from your on-site observations.

Good explanation Paul. One thing I wonder about in the L-39s is if the pilot training and/or judgement is as good as it could or shoud be. I am in unfamilar ground here, I wasn't at Reno, have only one brief jet dual jet flight in as Soko, and know little about L-39s. But I do know that they are heavily marketed, and one of the selling points seems to be how easy they are to fly and service. I would guess some jet racers are ex military jet pilots, but I wonder if others are at the low end of experience or training. If an L-39 is easy to fly, does that mean you have a lot of extra margin of safety, or does it mean it attracts less competent pilots? I think Bear or Strega or Dago are mostly flown by the cream of the crop. They better be, since they have a lot of maydays. And Ryan, they aren't at 380, I am certain both Bear and Strega have run at over 480 mph, and back when the speeds were valid before they computer boosted them. And just wait til Gary gets my spare Merlin in his Cassut, we just have a slight CG problem to solve.

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Bill Greenwood
Spitfire N308WK

From what I've been told, I wouldn't call the L-39 "easy" to fly. I would call it "straightforward", but the wing is very highly loaded and it was designed to train pilots to fly a very specific aircraft - the MiG-21, an extremely difficult aircraft to master. I've not gone in depth with any of the pilots I work with at the museum about it's stall characteristics, but they have said it tends to snap somewhat and it does so very quickly.

The items that I've been told on the L-39 that may give an idea of it's performance are:

1) Threshold speed of 125 knots.
2) 8-to-1 glide ratio with a best glide speed of 160 knots.
3) Lacks power. They all complain that anything over 2 or 3 G's, the airplane really loses speed. While it's capable of doing +8 G's, it can't do it for long.

I guess easy to fly is whatever we train in or get used to. Getch was talking about racing the piston Fury, and about being gentle and smooth in the turns and that any heavy G would drop off 100knots quickly. One thing about Reno, it sure seems to grab guys. Must be fun while you are in it.

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Bill Greenwood
Spitfire N308WK

Bill,

As jet warbirds go, the L-39 is a relatively easy, docile aircraft to fly making it attractive to a wider base of warbird pilot-owners, not just those with high-test flying experience. I would characterize it as the kerosene T-34 for comparison sake. Over the years, a number of guys that owned T-28s sold them and got into L-39s instead for the reasons you stated--low maintenance, extensive parts/tech support community, great reliability and for what it is, reasonably forgiving flight characteristics. IMHO, it does attract a notably less experienced pilot base, an airplane most can handle fine but a daunting undertaking for some. If it seems like you hear more about L-39 incidents/accidents than other jet warbirds, the big reason is there's so many of them flying (over 300 in the USA last I heard). As with all warbird types and classes, the quality of training, currency etc. for this type is all over the map. This leads us back to the bigger issue Doug R. raised on safety and training so I won't reiterate that here. I got no dog in this fight as far as jets racing at Reno but see no reason why they shouldn't next year. I'm sure the tragic accident will be looked at closely for any potential lessons to be learned. The unlimited guys do a great job employing safety practices successfully in a very challenging environment and I'm confident the jet racing side of RARA can/will do the same, though I believe their problem to be more a perception issue. A point to ponder--with the reliability of turbine engines, you won't see the engine failures in jets with the frequency in the other classes, if at all.

Well, I reckon I'm heavy enough to make the CG work out, I just don't have enough time between races to keep that Merlin running.

Gary

Bill you are right about that. I'm not sure what I was looking at when I got those previous numbers but in reviewing the data again it looks like 480s unlimted and 520s Jet.