Jet Engine Relights at High Altitude
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Join Date: Oct 2003
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Jet Engine Relights at High Altitude
Is there still such a procedure as a "Hot Relight" for jet engines at high altitude?
In my time at Boscombe Down in the late 50s during the hey day of the V Bombers we investigated the relight capabilities of jet engines at high altitude.
Soon found that if one could initiate a relight within 10 seconds of a flame out or shut down and whilst it was still fairly hot, reliable light ups could be achieved. After 10 seconds or so it would require a descent to medium altitude to achieve a relight.
The 201, or were they 102s, Olympus engines in the later Vulcans were superb. Had one up over 50,000+ and had no relight balks out to 10 seconds. What's more those engines would then slam accel from less than idle. Most impressive and Bristol received "a great credit to the manufacturer." bouchet.
We coined the phrase "Hot Relight" having the 10 second time limit.
Are "Hot Relights" still in the SOPs?
In my time at Boscombe Down in the late 50s during the hey day of the V Bombers we investigated the relight capabilities of jet engines at high altitude.
Soon found that if one could initiate a relight within 10 seconds of a flame out or shut down and whilst it was still fairly hot, reliable light ups could be achieved. After 10 seconds or so it would require a descent to medium altitude to achieve a relight.
The 201, or were they 102s, Olympus engines in the later Vulcans were superb. Had one up over 50,000+ and had no relight balks out to 10 seconds. What's more those engines would then slam accel from less than idle. Most impressive and Bristol received "a great credit to the manufacturer." bouchet.
We coined the phrase "Hot Relight" having the 10 second time limit.
Are "Hot Relights" still in the SOPs?
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Pilots are advised to try an immediate (new word for 'hot') relight as soon as a flame out is diagnosed in whatever position in the flight envelope. If it fails or the engine overtemps the engine should be shutdown and a normal or cold relight should be carried out within the cleared relight envelope.
During engine testing in the nineties, I used 10 seconds from shutdown for an immediate relight test and thirty seconds from shutdown for a cold relight, so yes, we still do it that way. However, modern FADEC control normally includes an automatic immediate relight facility, so the pilot has been taken out of the immediate relight loop.
During engine testing in the nineties, I used 10 seconds from shutdown for an immediate relight test and thirty seconds from shutdown for a cold relight, so yes, we still do it that way. However, modern FADEC control normally includes an automatic immediate relight facility, so the pilot has been taken out of the immediate relight loop.
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The Vulcan engines were the 201 series or the more powerful 301 series. I seem to remember the hot relighting went out of fashion for multi-jets, on the grounds that it was better to stabilise the aircraft and then analyse the possible reasons for the flame-out. Never had a problem cold relighting the Olympus at high level during airtesting.
The Avons on the Canberra were another matter... and low temp surges during slam accels at high level were exciting to say the least!
The Avons on the Canberra were another matter... and low temp surges during slam accels at high level were exciting to say the least!
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Yep
immediate / hot relight still in the emergency cards. My bird has auto-relight too. Once the flame has been out for more than a few seconds though - you stand little chance of a decent relight till mis 20's or below (ballpark jet A1 relight envelope)
immediate / hot relight still in the emergency cards. My bird has auto-relight too. Once the flame has been out for more than a few seconds though - you stand little chance of a decent relight till mis 20's or below (ballpark jet A1 relight envelope)
