Tornado 'Combat' Power Throttle Setting

[BluntM8]

Phil,

T6 is the turbine inlet temperature - if it is too high you can easily cook the HP turbine into an unuseable mess!

For interest, the general list is (IIRC):

0 - Ambient air.
1 - Air at compressor inlet.
2 - Air at exit of LP compressor.
3 - Air at exit of HP compressor.
5 - Combusting gases in chamber.
6 - Gas at HP turbine inlet.
7 - Gas at LP turbine inlet.
8 - Exhaust Gas.

Where Tn refers to the temperature and Pn refers to the pressure.

Don't be confused with N1 and N2, which are also refered to as NL and NH - the percentage rotation speed of the LP/HP spools.

T6NL caption, anybody?

Blunty (ready to be corrected!)

[flipflopman RB199]

Blunty,

That list is slightly different for Tornado, but I'll not be so pedantic as to attempt to correct you here!!

As I remember, the 34 Deg K at Datum/Low and 26 Deg K at Combat are entirely correct. With the DECU controlled 104, 25 Deg K TBT also equates to a 1% NH increase, and this is used when re-datuming the DECU to the ECU test bed figures. I remember on Post Inst runs ensuring that the TBT registered around a 25 Deg rise upon selection of Combat.

As goes the Datum/Low switch, the only time I can ever recall messing about with that, was during Post Insts on the 101 engined GR1's where the switch was left in the datum position for everyday use. As goes the worry of cooked engines, bear in mind that the engine was designed to operate safely and reliably with the DATUM position selected, and LOW is simply a cheap and easy way of stretching a little more life from the engines.

T6NL? Adour, if I'm not mistaken

Hallam Pilot,

I remember the blanking plate mod well, Also the subsequent mod to drill a 3.2mm hole in the centre, to try and alleviate the burst spray manifolds that began to occur!!



Flipflopman

[Obi Offiah]

There is confusion here between the datum/low switch which is:
1. Wire locked
2. Increases temperature and therefore thrust in dry power
3. Only very rarely used as the engineers/sooties get grumpy
4. Don't know if it gives extra on top of combat pwr (I spy a good staneval question!)??

Combat power is:
1. A detent post max reheat
2. Gives a bit more thrust
2. Can be used whenever you like (5 mins yadayadayada)
3. Rarely needed as the Tornado has so much thrust and great aerodynamics.

Hope that helps.

Please note that one of the above statements is a lie. If you can't work out which one, you should log off PPRuNe Mil forum immediately. zero/zero I fear this may apply to you!

So the Datum/low switch is similar to the Vmax switch which is also wired guarded. The exception is that Vmax only comes into effect when in Max AB and supersonic.

Judging by its name, Combat power I guess would only be needed when evading defences and during heavy take-offs, so I assume the restrictions are ok.

I wonder, has the triple spool layout of the RB199 been a factor in allowing the aircraft to have a Combat setting?

BTW Combat power point 3 is the most
accurate statement

[Obi Offiah]

Combustion Chamber Flame

This question doesn't apply specifically to the RB199, but does anyone know why at times a flame ring (like a very low power, low energy afterburner) can be seen deep within the combustion chamber, looking in from the rear (of course)?

Also what is a "blanking plate"

Cheers
Obi

[HallamPilot]

Also what is a "blanking plate"

Upon deselection of reheat, the priming, dump and shut-off valve (PDSOV) is closed, isolating the fuel system from the manifolds, but residual fuel in the manifolds is dumped over board on shut-down.

The blanking plate was a square piece of metal inserted between the joint of the reheat purge line.

This effectively blocked any fuel from being dumped overboard on deselection of reheat, thus stopping the plume of tell tale vapour.

This left residual fuel in the pipework and on a rapid reselection of reheat the residual fuel would ignite and cause a reheat surge.

As flipflop stated, this also caused the manifolds to start bursting due to the pressure on the system.

To stop this happening, some clever sort came up with the modification to drill a 3.2mm hole in the centre of the blanking plate. This allowed the fuel to trickle into the purge line, not so much to cause the plume, but enough to stop the surge.

[cornish-stormrider]

The triple spool was thought of to make a more effiecent and lighter engine, also having the contra rotating spools was thought to decrease the gyroscopic effect. In reality it was a much longer pain in the arse to rebuild, unnecessarily complicated, and still had that god-awful eyetie M12 with the interstage ring and the thermocouple wiring that was too difficult for the dog-lovers to deal with.

My training on the interstage ring was having several goes at it and my chorpscrawl slinging it in the bin -

I got there in the end though, the trick was making into a work of art.

[Kitbag]

The triple spool was thought of to make a more effiecent and lighter engine

And compact, look at other engines of the same period and power output and they are larger. The pressure rise across the compressor was also pretty impressive.

[BluntM8]

also having the contra rotating spools was thought to decrease the gyroscopic effect.

I believe, and no doubt JF will be able to elaborate, that the major design triumph of the RR Pegasus engine is that the HP and LP spools have identical angular momentum, although in opposing senses. Therefore, whilst the harrier is in the hover and gyroscopic effects caused by attitude change are competely cancelled out within the engine. Clever or what!

Blunty

[Obi Offiah]

Cheers

Thanks for the responses.

Obi