Vickers Viscount engine start

On the Concorde engines, it was said that when they were started a certain RPM had not be exceeded for a certain period of time as the main rotor shaft through the middle of the engine bent slightly during cooling after last running. To exceed this certain RPM too soon would wreck them until the shaft straightened (probably only a thousandth of an inch or so).
Can anyone verify this, Concorde experts? If so, possibly the same could have been true for the R-R Tyne engines in the Vanguard.

Quite correct. Can’t recall the exact details of use of engine debow, but it was part of the start cycle where the engine was held at a certain %age until the yellow debow light in the switch(es) went out, when the engine would then accelerate up to ground idle.

There are 4 debow switches on the FEO’s leg panel, and I THINK debow starts were carried out on the ‘turn-around’ and after the aircraft had been shut down for a shorter than specified time.

The low RPM on a Vanguard is just the engines in start position……it’s a very heavy propeller

When settled down to the correct figures the engine was set to high ground idle which meant not a gradual but a very quick acceleration to high RPM.

In that mode the prop was turning constantly at high rpm the throttles making small changes in pitch to give better control on the ground.

On take off the throttle went into flight mode and the RPM dropped away quickly followed but a much deeper sound as the engines spooled up in the normal fashion.

Hi All.

I seem to always remember hearing a clicking noise as each prop started to spin on the Darts of Viscounts. Can anyone explain what this noise was, I assume something to do with igniting the fuel.

Also On the Vangaurd start up, why did the pilots seem to allow all four engines to idle then gradually increase the rpm on each engine ready for taxi power

Thanks in advance to any replies

Regards
Nordjet415

Indeed the clicking would be the igniters.
Turboprops have poor acceleration by their very nature. The Dart in particular because all the moving parts are fixed on a common shaft, which means there is a great deal of mass to get moving. If you try and accelerate it too fast you could get overfuelling and a surge. For this reason the RAF don’t test the acceleration time of a turboprop.

On the Concorde engines, it was said that when they were started a certain RPM had not be exceeded for a certain period of time as the main rotor shaft through the middle of the engine bent slightly during cooling after last running. To exceed this certain RPM too soon would wreck them until the shaft straightened (probably only a thousandth of an inch or so).
Can anyone verify this, Concorde experts? If so, possibly the same could have been true for the R-R Tyne engines in the Vanguard.

Would that be the same for Vulcan engines?

Viscounts Start-up

Yes, I’m sure the clicking noises were igniters (IIRC they were referrred to as Cracker Boxes).
The Vanguard pilots were probably waiting for certain temperatures and pressures to be attained on each engine before winding them up individually for a power check.
On the Concorde engines, it was said that when they were started a certain RPM had not be exceeded for a certain period of time as the main rotor shaft through the middle of the engine bent slightly during cooling after last running. To exceed this certain RPM too soon would wreck them until the shaft straightened (probably only a thousandth of an inch or so).
Can anyone verify this, Concorde experts? If so, possibly the same could have been true for the R-R Tyne engines in the Vanguard.

Don’t know the Vanguard, but on the Viscount it was definitely the igniters making the clicking noise

The first part of your question could have been the Torch Igniters doing their stuff, as you suspected.

Although I’ve no experience with multi-engined types, perhaps it was a case of prudence to run each engine up individually to ensure that the brakes would hold………..