Hot Start Video
 

YouTube - 737 Engine Fire

I've heard this is done on new engines, or would it be a case of fuel flow being switched on before N2
Either way I could imagine the passengers looking out, being a little concerned seeing a 737 with after burner !
Pretty cool though :D

Not particularly sure if this is a 'hot start' per say. Possibly the later result of a 'wet start' where the residual fuel hasn't been motored through the engine. Result- a rather impressive flame!

Pretty certain...
 

... that that's a new / recon engine being run for the first time. There is an awful lot of protective oil that get's burnt off, hence the smoke and the flame. That might explain why it is being videoed, and what is clearly an MX engine run.

I'm sure an engineer can pop in and confirm it / tell me I'm wrong.

DW.

I have not worked on an airline but as a sootie I would say that that was a very stupid thing to do. If you look at the flame, particularly towards the end it is at the bottom of the jet pipe. This is because the fuel puddles there when you have a 'wet start'.
If you have cranked the engine over a few times with the fuel valve open you can fill the combustion chamber. Most of this will fill a drains tank that will empty through a pipe out the back of the engine. (You can see this right at the end of the video).
The easy way to clear this fuel, and the lazy way, is to just start the engine and burn it off. The proper way is to drain the tank and dry crank the engine to clear the residue.
Of course, they may have simple of had a start up snag that cleared, (although I would not have sent the aircraft out without investigating it first)!

Inhibiting oil very rarely lights up, you just get a hell of a lot of smoke followed by possibly a small flame and slightly higher start temps. Again, this should be avoided by bleeding the fuel system first. This is almost certainly fuel coming out.

After a #2 Engine change on G-MONG i was tasked with running the installed engine, i wet motored it over for slightly longer than the recommended time with the same result as the video. Still the EGT wasn't exceeded and no one panicked, the guys outside said it looked quite impressive particularly as it was 2 O clock in the morning. It has to be said though that the CFM56-3 on the 737-300 is prone to torching after a engine change, i've seen it several times.

It is actually the safest thing to do, once ignition is on you have 2 choices, blow it out or deal with a fire that burns upward as opposed to aft.

Usually the result of residual fuel from a maintenance action or failed start attempt (ignition). It is really quite common.

737-300 normal on new engine. Very impressive at night.

My point entirely. Any cabling running along the flap falsework would not exactly enjoy being heated up by the upward blowing flame for that sustained period. Any manual that I have read does not subscribe to starting an engine suspected of having a flooded engine in that way. A jolly jape, a bit of a laugh and very impressive, (call it what you will), what about the rest of the aircraft?

I had an instantaneous light off on a 744 once and tail pipe fire, easy enough to deal with, fuel off continue to motor etc.

We also had a tailpipe fire on a 747 classic once (not me) because of a communication problem (english crew, chineese ground crew) the crew dealt with it incorrectly, unfortunately by the time the crew realised what it actually was, wires had been burnt through and they were unable to shut the engine down/put out the fire from the cockpit, lots of damage, fortunately no-one hurt.

I can't actually view the video (youtube banned here!) so can't comment on it, in the good old days used to get a bit of a flame on the JT9 on strating but not much to worry about.

Is that preservative fluid being only doubt on the duration.

Variation on a theme.

http://i21.photobucket.com/albums/b270/cumpas/BR2.jpg