Question about hot starts

[vololiberista]

What constitutes a hot start? When I read the manuels I see conflicting information. For example it says max hot start for the Super is 595c. In the same manuel there is an addendum that requests placarding on th EO's panel showing 650c. The Sultan's a/c at Brooklands has 690c placarded!! so there seems to be quite a range. Assuming let's say 595c, would that be from a cold situation on an ISA standard 15c or more? Obviously during a stopover the initial temperature would be higher.
My feeling is that the Top Temp controls would be used quite frequently.
Another question arising from this is that the manuels also state that max ambient temperature for starting is 50c. What then would be the procedure at say Kuwait in the Summer where the temperature would be 54c?

vololiberista

[Laurieg]

Merry Christmas

Depending on your perspective a hot start could constitute anything from a higher than normal 'light up' temp through to high peak EGT.

It all comes down to reducing the stress loads on an engine. The engine start is where the most thermal and shock stresses occur, (along with rapid accel/decel). This becomes one of the major factors on engine life. At higher temps turbine creep is one of the stresses can occur which will lead to excessive blade wear/failure and performance. Even thogh the flight deck guages indicate Engine Gas Temp the controlling factor on the turbine is TET, (Turbine Entry Temp). This being hotter than EGT, keeping EGT at lower controlling temps will ensure TET never gets exceeded.

All our engines controlled at 595 EGT but you can have a momentary swing to 690 (2 sec). Even 595 EGT was limited to 5 mins (TO power). Due to differing MOD states of engines we used to have placards on Panel B indicating that state but these were removed some years ago as all engines were deemed to be at a level condition.

Initial starts could be slow/hotter than usual but this had nothing to do with the engine itself, (the first start (#3) could be slow because you were using the APU for air at 40 psi. Subsequent starts had the mass flow from the other engine/s for a more stable run up.

More often than not the EGT would not reach top temp in ISA conditions, (tended to stop around 510 - 530), but an occasional swing to 610 was not unusual on first installation runs.

I have been involved in numerous engine installation runs in hot/high conditions and although #3 could be slow to start on the APU, in such conditions you used your experience to decide if the start was going to be successful with reasonable limits. The rest of the starts tended to be normal due to, again, the mass flow thus quicker starts. The same applied to cold starts although these can be a bit smokey due to the oil seal being effected by the temperature. Again, it is down to the operator to decide if it can continue.

Turnaround times were normally scheduled to minimise stays in these temps.

Basically, it is all down to keeping the engine stresses down to the minimum. However, when necessary the all engines are robust enough to take very limited excesses.

[vololiberista]

Thanks for that. Your explanation is pretty much how I thought.
Merry Christmas to you too. Or Buon Natale as they say here! Currently recovering from 2 glasses of Nocino ( a liqueur made from chestnuts!)
vololiberista

[Manofmendip]

Hi chaps

This is fascinating stuff, it really is.

I hope that temperature issues will not be too much of a problem at Brunty, with the 'ground runner' and the 'flyer' aircraft projects.

On another subject I must apologise, Nicholas, for omitting Italy as a country where we have a 'VC10der Loving Carers' member, in our recent newsletter.

Best regards to you both.

Dave

[vololiberista]

Hi chaps

This is fascinating stuff, it really is.

I hope that temperature issues will not be too much of a problem at Brunty, with the 'ground runner' and the 'flyer' aircraft projects.

On another subject I must apologise, Nicholas, for omitting Italy as a country where we have a 'VC10der Loving Carers' member, in our recent newsletter.

Best regards to you both.

Dave

I would think Brunty reaching the heights of ISA would be cause for a celeb!!! Especially in current UK weather conditions!!

LIMZ would be a good place for a refuelling stop unlike LIRP which apparently has been used. As LIMZ has no noise abatement (just a speed/height limit and a turn). The largest a/c on the field up to now has been a B757. A VC10 would top that I think and would I bet be airborne before the taxiway A rwy intersection. Non of the 73's even those of Ryanair can do that!
vololiberista

[Laurieg]

No problems.