Single Engine Taxi

jchronic · #1 04-19-09, 09:55 AM

Greetings All:

Brand new to the Forum and looking forward to learning much more about this airplane from the experience evident on this site. I've been flying both a 336 and a 337 on marine mammal surveys for about a year, and thoroughly enjoy the airplanes.

Question: Having a minor disagreement with my flying partner; he gets uncomfortable when I shut down the front engine and taxi on the rear only. Is there any reason why this is unsafe and/or a bad practice?

Thanks-
Joe C.

hharney · #2 04-19-09, 10:16 AM

I do this is certain cases, primarily when I have landed and I taxi up to a tarmac while being directed by ramp personel. It is just a safety courtesy for the line crew as the aircraft is parked. I won't do it when I taxi out for take off, obvious reasons. Some considerations when doing this, the rear engine oil temp will rise faster than the front during prolonged ramp times. During long times on the ramp, especially while not moving, the rear engine may reach max oil temp before the front. In these cases I have shut down the rear. The first incident that comes to mind is departures at Oshkosh. Not sure your specific case but these pratices are fairly common for the Skymaster.

John Hoffman · #3 04-19-09, 02:59 PM

If I suspect the taxiway/apron could be dirty I wouldnt hesitate to shut the front down to taxi in but taxi out for takeoff with both engines for the reasons Herb has mentioned.

Ernie Martin · #4 04-19-09, 04:55 PM

Aside from temperature issues and the risk of takeoff on a single engine, no reason why you can't taxi on a single engine. Regarding temperature, I often taxi out on only the front engine in Nassau, when I see a long line of airplanes taxiing ahead of me and the tower comm suggests many inbound. And of course it's always hot. So the heat and the wait simply don't permit for the rear engine to be on. I wait until I'm second for take-off to start the rear engine and my reminder is that I never do the pre-flight 1800 RPM checks on either engine until then, until both are running and I'm at the head of the line.

Ernie

skymstr02 · #5 04-19-09, 06:49 PM

Just think of this--the only cooling air going to the rear engine comes in thru the scoop on top of the cabin. The only way that air flows into that is to be pushed by the front prop, or air/ground speed. The rear prop doesn't suck enough air to flow around the cylinder cooling fins. You could be damaging the engine by localized heating that is not read on instruments on the panel.

Taxiing in with the front engine running is no more dangerous than taxiing in in a 182 or a 210.

Dale Campbell · #6 04-20-09, 01:15 PM

I fly from a short and somewhat dirty field. The runway is paved but nothing else is paved. I start both engines on my concrete pad in front of hanger that I know is clean. I sit there until the engines get into the green. I then put the front engine at idle and use the rear engine to power me to the runway. I do my run up where the runway is clean. After landing I shut down front engine as I leave the paved runway to taxi back to hanger, so front engine does not kick up dirt and drive it into rear prop.

John Hoffman · #7 04-20-09, 10:41 PM

That was my thought re. shuting/or idiling the front engine. Being able to taxi with that rear engine mounted up high is just another Skymaster standard benefit.

stackj · #8 04-21-09, 01:02 AM

We tend to taxi out on the front engine only if we expect a long delay.

We arrive (to the line person) using only the rear engine. This is a short run on the rear only and is for the protection of thr line person. (Oh, by the way... they sometimes look at you a little funny when you shut it down a long ways away from them. We have had the lineman turn around and walk away--- then suddenly realize that you are still moving - and without a front prop turning)

Ernie Martin · #9 04-21-09, 10:48 AM

Jim's tale of the lineman reminds me of two about the Skymaster. Both happened in the Bahamas, on remote islands.

Landing at one airport, where a landing fee applied only to twins, the collector looked out at the aircraft and asked "What's that a single or a twin?" and I said (with a straight face) "It's a single -- the one in the back is a spare."

On another trip, the lineman asked "How come one engine facing one way and the other facing the other way?" and because of the way the question was posed I couldn't pass up this answer: "I use the front when going East, the back when going West."

Ernie

jchronic · #10 04-21-09, 09:52 PM

Thanks for the responses, gentlemen. I couldn't imagine why there would be a problem, but when I found this forum, nothing like asking those with more experience. In addition to taxi-out/taxi-in, we do a fair amount of ground repostioning with our survey airplane, taxiing hangar to terminal to pick up our scientist crew in the morning and vice-versa after the mission. Seemed unnecessarily cumbersome to start both engines for that.

Roger · #11 04-24-09, 01:36 PM

I taxi around a bit on the rear to get from the fuel depot to the hanger, etc.. Overheating hasn't ever been much of a problem. That being said, the one thing I always do is shut off my avionics master before I start/re-start the 2nd engine, just to prevent a power surge from frying something. Anyone have any thoughts on that?

It is a bit of a pain because all the radios, gps's etc.. have to come back on line

edasmus · #12 04-24-09, 07:53 PM

I concur with you Roger. My 1973 G model has an avionics buss interupt feature that will do this automatically anytime an ignition switch is moved to the start position but I figure "why tempt fate."

Ed

Dale Campbell · #13 04-29-09, 09:00 AM

Hi Guys,
I was taught to always start the rear engine first then the front engine and last turn on avionics. When shutting down, first turn off avionics then front engine and last the rear engine. That is what I always do. The front engine is shut down as I leave runway at small fields but at larger airports as I arive at ramp. Dale Campbell

Ernie Martin · #14 04-29-09, 10:11 AM

My starting procedure, which I believe is based on the POH, is the reverse: front engine first. The reason for this is important, and I think this procedure has saved the day several times. The cable run from battery to starter is much shorter, probably 3 to 5 times shorter, for the front engine, so the electrical resistance and voltage drop is much lower. There have been a number of times when, after not using the aircraft for several weeks, the voltage at the front-engine starter was so low that it barely turned the engine, and it was just enough to get the engine started. At times cranking would stop after a couple of engine turns, when battery voltage dropped too low, and it was lucky that after letting it rest for a few minutes, the engine caught on the first turn of what was obviously a dying battery. In most of those instances, I believe the rear engine would not have started, and switching to the front one would not have worked because the attempts at starting the rear engine would have dropped the voltage even further.

I hope others will jump in and comment.

Ernie

Dale Campbell · #15 04-29-09, 01:14 PM

Hi Ernie,
You are correct, the manual states front first. Again the airport I fly from is dirty so I am very sensitive to puting debrie into rear prop. I also have a battery charger/maintainance devise that is always plugged into my battery, so low battery from sitting is no longer a problem. I have had stones, screws, sticks and even a chunk of aluminum cowling hit the rear prop. The upper rear 1/2 ring cowling front of prop is in shop as we speak getting replaced with new carbon fiber because it cracked off and hit the prop. So thats why I start rear first and then the front. My rear engine always start easier then the front for some reason. That is another reason for my starting proceedure. Dale