Shutting down No 1 engine to increase endurance

[ConwayB]

Hello all,

I may be doing some prawn spotting soon in an O-2A which requires maximum endurance on full tanks. This led me to wonder about a technique that tuna spotters used in their operations in South Australia, namely shutting down the front engine and cruising on the rear engine.

Flight times of 8 hours and more were commonplace and, when time is money, that was quite lucrative.

However, I am the owner/operator of my aircraft - unlike the tuna spotters - and I have ABSOLUTELY NO INTENTION of deliberately shutting down a perfectly serviceable engine during the proposed prawn spotting... but it led me to wonder if there are any 337/O-2 drivers who have experience in this technique to increase endurance? What were your fuel flows and endurance figures and airspeeds? What detrimental affects did it have on the aircraft?

Thanks in advance.

Cheers

Conway

[skymstr02]

Have you intentionally shut down and engine in flight? Performed an air start? After a restart, how long go you warm up the fresh started engine before you can apply usable power--the engine will get cold soaked with the 90 kt wind passing over the cylinders not producing any heat.

[ConwayB]

G'day,

To answer your question, no I haven't intentionally shut down an engine in flight except during the training sequences.

As I said, I have no intention of doing so, but was wondering what sort of endurance, fuel flow, speed figures others have achieved.

I have the Cessna figures (the usual lies you find in a POH) and I have the USAF figures (which are more realistic) for normal operations and so can guess at what the 'emergency operations' figures are.

It was common practice for tuna spotters to cruise on just the No 1 engine and put in 8 hour sorties. I would guess that starting a cold engine in flight would not be conducive to engine longevity.

CB

[Learjetter]

Lots of single-engine performance and opinions at this thread:

http://www.337skymaster.com/messages...ead.php?t=2704

[jchronic]

I haven't done it and have no need to do it intentionally, but an opinion on a couple of your questions:

1. Endurance: Should be easy enough to figure if you want to test it by shutting one down at a comfortable altitude (overhead the airport?), establishing the speed you want for fish-spotting, and checking fuel flow. Alternatively, WAG it by figuring (conservatively) a 30-50% increase in fuel flow. I'm assuming you're normally throttled back pretty far while spotting?

2. Engine wear: Likely some additional from a cold start, but not much different from starting on the surface without preheat on colder days. I would let the restarted engine idle for at least five minutes with cowl flaps closed before s-l-o-w-l-y increasing power.

I don't know how much endurance you're ultimately looking for, but until a couple of years ago we had been flying 6+ hour marine survey missions with very comfortable reserves using full mains & aux tanks (100 knots GS on the survey tracks). Finally backed off to 4:30 max with full mains only for personnel comfort (pee breaks).

Joe