[books] aircraft and engine

Ron Hardin wrote:

Well, you've got this combustion chamber, and you add fuel, and
ignite it.

It's open on the front and the back.

Why doesn't the combustion product simply blow out the front and
the back both? Leaving you sitting on the runway exactly where
you started.

The buzz bomb solved this in the only sensible way. The vanes shut
and then you blow up the fuel. So the Germans saw the problem.

Starter motor (electric or otherwise) starts the blades spinning to get
the sucking and blowing cycle geauxing... Don't introduce fuel and
ignite it until adequate RPM's are established...

Quote On
The process for starting a gas turbine engine is a complicated procedure
which requires continual monitoring of various engine parameters to
avoid damaging engine components. One potentially damaging condition
which may arise during engine startup is a hot start. The exact cause of
a hot start condition in a gas turbine engine has been the subject of
much speculation and theory, however, the detection of the occurrence of
a hot start condition is well known.

A hot start condition occurs when the temperature of the working fluid
exiting the turbine section of the gas turbine engine exceeds, by a
certain amount, the expected exhaust gas temperature schedule for the
engine during a normal startup. As will be appreciated by those skilled
in the art, an unaddressed hot start condition can cause the gas
temperature in the turbine section to exceed allowable material
temperature limits, thereby shortening or ending the life of internal
engine components such as blades, disks, seals, etc. Typical engine
starting procedures therefore call for careful monitoring of the exhaust
gas temperature, and immediate shutdown of the startup sequence should
exhaust gas temperature exceed the appropriate limit.
Quote Off

MediVac helicopter pilot had a bad day here at the local airport awhile
back. Landed for refueling and then toasted one engine on restart.
Couple days later, they replaced the engine (and probably the pilot) and
left...

As I am told, Garret engines are cheaper but more prone to hotstarts.
Computer control has made it more foolproof, but also more costly...

The History of Engines - How Engines Work
Part 2: A Short History and Timeline of Gas Turbine Engines
http://inventors.about.com/library/i...gasturbine.htm