Safest for your 503 descent method.

[nickjaxe]

Hi all been asking around about this subject...I wonder what you guys think,

Ok your in a trike it has a fan cooled 503DC, your at 2500ft and need to descend to 500ft....what the safest way of doing it for your engine ie to avoid seizures, ect,

Part throttle say 4000rpm and come down gently......or power to idle and give it bursts of power every 30 secs or soon the way down.

Nick.

[kloot piloot]

The Lycoming guys call it "shock cooling". The ideal is to settle into a controlled descent wilst slowly reducing revolutions.

Pedal off to 4000 rpm and power glide it home.

I have heard of a 4000ft idle descent and when he needed power, the engine had cooled down enough to require choke.

See no reason for 30 second bursts, if you can gradually reduce temps with coming of the throttle slowly.

Blik-aeries control temps with fuel-mix, 2-strokes no such luxury. However 4 strokes are more prone to shock cooling.

[John Boucher]

http://en.wikipedia.org/wiki/Shock_cool ... engines%29

[Biggles]

The function of the fan and the cowling on the 503 is to regulate block tempratures. So throttling back means less forced air into the cowling and less cooling.

AFAIK if going from straight and level you should be able to pretty much throttle back completely. But when having just finished a climb level off at cruize speed to let the temps come down from full throttle temps before decending.

[Tumbleweed]

Think the 30 sec boost is for carb icing.

[nickjaxe]

Biggles that make good sence.

Nick.

[Morph]

If you have egt probes, throttle back to a nice cool spot, where the engine will be running slightly rich, as opposed to a hot spot, where it is running lean.

If you are in a situation where icing can occur, throttle up every 5 minutes for a short while. If the engine runs rough for a few secs, that means it is ingesting the ice, not a problem, it will smooth out again. If there is ice, reduce the time gap, if nothing, increase the time gap.