Early Merlin Neg-G Engine Cutout

[cbxsteve]

As you may know, early Merlin powered aircraft, before the installation of "Miss Shilling’s Orifice", would cut out upon pulling negative Gs due to the carburetor fuel feed design.

What I almost learned the hard way (and it's logical), is that the engine will not restart itself unless there is sufficient airflow through the prop to "windmill" start it.   Flat spins,  snap rolls, terminal phase vertical target fixation, etc. do not constitute conditions under which the engine will windmill restart, so you might want to keep the location of the "E" key in mind if you fly as crappy as I do, so you don't stab three other keys before finding the right one.

[SmokinLoon]

Interesting.  I've not done any of those moves in a Hurricane, I've always been moving along real good when I've nosed down and it cut out.  I've not ever had an issue with it starting back up.  Just for fun though, I'll be doing a few of those negative g's with no E to see if I can get it to go that far.   

[Fish42]

As you may know, early Merlin powered aircraft, before the installation of "Miss Shilling’s Orifice", would cut out upon pulling negative Gs due to the carburetor fuel feed design.

What I almost learned the hard way (and it's logical), is that the engine will not restart itself unless there is sufficient airflow through the prop to "windmill" start it.   Flat spins,  snap rolls, terminal phase vertical target fixation, etc. do not constitute conditions under which the engine will windmill restart, so you might want to keep the location of the "E" key in mind if you fly as crappy as I do, so you don't stab three other keys before finding the right one.

Not quite true from what I remember, its not the speed at which you are traveling but simply the time the motor has been off. Try a spiralling neg G dive and even with the airspeed over 200 it needs to be restarted manually.

At low speed this takes as long as it does to start on the runway, at higher speed it starts quicker.

BTW to restart you must be at .5 neg to Pos G.

[icepac]

I've got a tough enough time even getting any prop to stop in aces high.

They seem to windmill to 50mph or slower airspeed.

[SmokinLoon]

I took the Mk I up and got it to cut out just as I went nose backwards and tail went up... the engine was dead and the prop stopped.  So there I was stalled out with nose and tail parallel to the ground at 10k.  Nothing worked to get my nose down until I popped flaps and put the gear down.  Luckily my nose went down and the engine started up.

It is a for sure thing, that maneuver can be dangerous when in combat.    

[cbxsteve]

Not quite true from what I remember, its not the speed at which you are traveling but simply the time the motor has been off.

Interesting, I shall experiment further.

(20 minutes later) And I just did.  It is in fact the windmill issue, and not time.  I took a Hurri I up to 2k, inverted (engine stalled), and did a 150kias decent to 200ft (long time).  When I flipped upright the engine started. I repeated this at about 100kias a couple of times...same result. I then tried a couple of hammerheads with a neg G component near the top, and the engine still restarted after I went nose down (grrr). As a last ditch effort I started another neg G hammerhead, but kept the nose pointed at the sky way past when I lost rudder authority...bingo, the prop stopped spinning and the engine needed a restart.

Seems the need for restart is definitely linked to a lack of windmilling.  The airspeed indicator was somewhere well off the scale south of 40kias before the prop stopped spinning though. Seems a stiff breeze will keep it spinning, but who knows what the real number for a fixed pitch prop on a warm Merlin would be.

[icepac]

Planes landed on the cv will windmill.

[Krusty]

CVs travel over 40mph when the fleet turns, so that's understandable why planes windmill on them, and why it's impossible to chase them in PTs or fire torps from a rear aspect.