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Voodoo 3
26th Jul 2011, 09:40
Afternoon,

Recently I was taxying behind an An 124 when before entering the runway the pilot mentioned to ATC that he would need four minutes on the runway for 'engine stabalization'. Neither me or my colleague had ever heard of this request before. Sure enough a long delay ensured to allow for this amount of time on the runway.

Why is such a very long run up time necessary. I guess it is due to the type of engine fitted as surely if they were fitted with RR or GE then they could just spool up and go. Judging by the tailplane there must have been at least 50% thrust, possibly more during this run up. Why couldn't Ivchenko (who I believe designed the engine), build one that could spool up to maximum power in one go?

Maybe Antonov could have fitted RR or GE in the first place. But possibly that isn't a very Russian thing to do!

galaxy flyer
26th Jul 2011, 13:56
My understanding is that the engines were reverse engineered from CF-6s that were capttured when the Soviets took Kabul in 1979. However, they were unable or did not have the metallurgy to achieve the high temps of the original design. That said, the TF-39s on the C-5 a similar procedure on standing take-offs, but the time was 25 seconds.

WHBM
26th Jul 2011, 22:12
Maybe Antonov could have fitted RR or GE in the first place. But possibly that isn't a very Russian thing to do!

The Antonov 124, like it's Antonov 22 prop-driven predecessor, was originally designed primarily as an ICBM carrier, to move them round the Soviet Union from the central missile base at Tver (halfway between Moscow and the old Leningrad), where the remaining Russian Air Force fleet is still based. They would fly them to dispersed airfields from where Mil-12 (very) large helicopters would take them individually to sites hidden in the forest. Commercial airfreight haulage for the An124 came later.

Due to this, it is unlikely that RR or GE, both from countries where said cargo was doubtless targeted, would be particularly permitted by their respective governments to supply engines for such a craft.

Incidentally, the Antonov design organisation was, and still is, a Ukrainian company, not Russian.

chevvron
27th Jul 2011, 03:21
Yoi were lucky it was only 4 minutes, originally it was 10. This was demonstrated at its first appearance at Farnborough; it lined up for its display but rolled before the engines had stabilised resulting in a compressor surge which necessitated a new engine being flown in, with the Antonov 22 turboprop bringing it nearly landing on the grass next to the runway!!

isaneng
27th Jul 2011, 15:05
'We' use the big Antanovs on a regular basis, and this is a standard requirement for them. I believe their slow spool up time is a byproduct of their design timing - they were some of the Russians first 'big' jets which suffered from compressor airflow problems during acceleration (I think). Certainly I've seen/heard one 'pop' an engine whilst lined up and subsequently start its run up time all over again (no, they didn't taxi back....). Have also heard that they talked of fitting RB211s to later models, and a quick 'Google' confirmed that, but no idea if they ever did. We've also used the An 225, now that was impressive!

grounded27
28th Jul 2011, 01:57
I was in Managua Nicaragua beside a 124, I wanted to head over and check out te aircraft and crew but as time fell short they were closing up. Seemed like forever for them to get all engines started for taxi. Thrust up for taxi I saw a large spark and a security shack crumble a far distance behind. On the runway for takeoff I whitnessed the same long power up to set thrust. It was early dawn seemed like they clipped the fence dissapearing at a very low altitude.

Tarq57
28th Jul 2011, 02:44
Many years ago one of these beasts came into Auckland.
I was working in Wellington, and saw the incident report on the AFTN.
It read as though the crew had decided to perform a beat-up of Auckland and a low level circuit over the city to come back and land. Communication difficulties were mentioned.

Found out later these guys were simply overshooting. They hadn't received a landing clearance at four mile final - which unbeknown to the tower staff was the cut-off point for them, so invoked the lengthy and complicated procedure to overshoot. This involved the crew reconfiguring the aircraft for minimum drag at whatever airspeed they were able to attain while the FE gradually coaxed the engines up, a tiny bit at a time. By the time they got to the runway they had enough thrust to level out, after the "low pass"- which was apparently about 50' - they had almost enough thrust to climb, after a fashion.

Apparently they crossed the city at about 500', in a rather shallow climb. Much noise and smoke. Makes you wonder how they'd cope with a windshear on final.