Single-engine Endurance and Performance

[Cole5Oh5]

Load it up, then fly it the way you want. Fill it with sand bags, cement bags (they are readily available). Put in as much or as little fuel as you want. Then take it up to 5K, and shut down an engine. Don't go pansy on us, using the zero thrust thing, shut the engine down. Experiment with the various power settings. Then shut down the other engine. Oh, you might want to fire up the one you shut down first.
See if you can hold altitude at 2300 and 17 inches. Then move up from there.
Do the test pilot stuff your self.
Let us know if how you do. See if the POH can be ignored.
Make a video of all this, too. You can mount a camera so it shows the instrument panel. Looking over the left shoulder.

[hharney]

By the book, it works,

My Vote is YES

[edasmus]

Ernie,

My two cents.... Be careful out there. If you are going to start feathering props, start at very light weights and work up from there. And what the heck, you may as well do it over the top of a 4000-5000+ foot runway just in case things do not go quite as planned. I'm just a fan of being conservative. It keeps us safe and keeps our old machines flying. The results would be interesting, however I personally believe the book and assume that is the best case scenario. I figure I would not do as well as the book because my airplane and my skills would not match the airplane and the pilot that Cessna used. Be safe.

Ed

[Ernie Martin]

Appreciate the inputs. Hoping to do it late this week. Sorry, but I will do it via the zero-thrust simulation, and yes, on top of a 4000+ runway. I also believe the numbers, adjusted of course for aircraft aging which reduces thrust and increases drag, thus my 2/3 load. Will let you know.

Ernie

[Cole5Oh5]

This is supposed to be a valid test.

Do it over the water. See what happens. It's amazing what a little reality dose does to your pucker factor. And the validity of your test.

[tropical]

Just a side note on "zero thrust" settings. Even if you have set the book "zero thrust setting" you are still producing a small amount of thrust.

The airplane will behave differently. Try it with "zero thrust" then go back and feather the engine. It's an eye opener.

[Jim Rainer]

I vote YES:

Normally aspirited '76G; FE prop feathered ;4200 +/- weight; summer; 6,500;TAS 115K +/-; 24/24; actual flight from GPT to AWM after losing front engine SE of GWO - continued to AWM. No sweat; opened RE cowl flap 1/2 but don't think it was necessary.

Took a mountain flying course with a United instructor who wrote the book on mountain flying over Leadville, CO; summer; again about 4200lbs at about 11,000 and he asked if it would sink quickly or slowly. Told him I did not kow so he simulated zero thrust and to both our surprises, it mantained altitutde!! We didn't do this long enough for a true test but we both thought it would start down at least 500' per min.

[jchronic]

I vote 'Yes.' It's true that the POH numbers were generated on the basis of a new, clean airplane flown by a factory test pilot (and such computer data as was available in the 1960s). But from what I remember when I checked the performance numbers when I started the marine surveys a few years ago, I was comfortable I could get back to dry land on one engine, even with an airplane at near max gross (4200#) - bearing in mind that I'm talking about already being at 700' when the engine craps out.

Even if your airplane is so out of rig or dented that you couldn't maintain, say, 5000,' at max continuous (25/25) the sink rate should be minimal, down to a point where you'd be in ground effect. That would cover a lot of ground (or water).

Regarding the engines, I'd start at the top of the green arc and see what it gave me. If the airplane wasn't holding altitude, I'd let it sink until I wasn't comfortable going any lower and then use it all. A good reason to baby the engines under normal circumstances.

All of this is analogous to the 'driftdown' procedure we used in the airlines on the heavy jets.

Finally, unless you're alone, don't forget about throwing stuff out the cargo door (women and children first?)

Ahab

[WebMaster]

Have you done it yet, Ernie??

Inquiring minds want to know.

[Ernie Martin]

Hoping to do it this weekend.

Ernie

[billsheila]

I did this when I went flying in N2131X with the Terrafugia boys who wanted to learn some things about Skymasters and "blown elevators" (as their test pilot referred to it) and as they were toiling with getting the flying car going. In that case we were pretty close to your question, except for the temps, which were right around standard.

Max gross, front engine set for zero thrust. It would fly along all day long at 25/25 on the rear engine at 5000. I have only done a more legit test once when I mistakenly ran the rear engine out of gas. I didn't mess around with gathering data that day, as I was IFR and got it going again in about 20 seconds!

Bill

[Ernie Martin]

I did a simulated and brief test on Friday. I conclude, guardedly, that the answer is Yes. I say guardedly because I did it with passengers on board, approaching and slightly overshooting the destination airport, for about 10 minutes. It seemed to maintain altitude with the front engine at 25/25, rear engine at simulated thrust with the adjustment for hotter day, and the front engine temperature seemed to plateau at an acceptable level, without overheating, despite having the cowl flaps only half open.

I say seemed because one cannot say with absolute certainty that I wasn't losing a few feet of altitude or the engine slowly increasing in temperature. It didn't seem that way, but I would have liked to have run the test for, say, 30 minutes, and to do that safely (for me, anyway) I would have to orbit an airport. Couldn't do that with my passengers.

What I can say with reasonable certainty is that any loss of altitude, either because it was undetected or resulting from later having to open more the cowl flaps later for engine cooling, would be minimal (e.g., 25 ft/min would give you over 3 hours of flight from 5,000 feet).

Will be away for over a week without regular Internet access, so there may be a delay in answering any queries.

Ernie

[hharney]

Single Engine Trials
Sunday June 6, 2010
C337 N712JF C Model N/A

Main Fuel Tanks - 90%
Occupants - 2 adult male
Misc items in baggage area
Estimate the load to be 50% of gross


Rear Engine Power - Front Engine Feathered
2500 RPM - WOT
5500' MSL - 48 F - 100 FPM - 112 IAS -
6000' MSL - 48 F - 200 FPM - 107 IAS

Front Engine Power - Rear Engine Feathered
2500 RPM - WOT
7000' MSL - 47 F - 200 FPM - 90 IAS

We continued to climb to 7500' MSL and then decided to re-start the rear, would not start. After trying several times I looked over at the AMPS and they were pushing 30. I am not sure why the rear would not turn over. When I engaged the starter it would only move the prop 1/2 a turn and stop. I waited at 7000' MSL until the battery came back to a balanced level and tried it again but no good. It would not turn over out of feather. By this time we have been flying along on the front for about 25 or 30 miles at 7000' MSL. We turned right 90 degrees to a 012 heading for Newman's field and started a descent through a hole in the clouds. The single engine approach was uneventful. Given the front engine was the only engine making power the gear was normal and retracted without using the hand pump. It was a great landing on the turf field at Newman's and taxied up to Larry's hanger with only the front engine. After pulling the cowl on the rear and not seeing any red flags I buttoned her up and jumped in the left seat. Started the front, OK no problem. Voltage and AMPS look fine, started the rear, OK no problem, fired right up like normal.

What happened? Why would I not be able to start the rear in flight? The front started fine. I have the MT props, don't know if this has anything to do with it. Starter is getting compromised maybe? Battery lead is weak? It was really surprising when this happened but a good exercise and everything turned out OK. If anyone has had this happen please let me know your thoughts.

[skymstr02]

Herb, did you advance the prop lever to the high RPM stop from the feather position on the altitude re-start?

I've caged both of mine at altitude, with sucessful re-starts, but I have the stock McCauleys and unfeathering accumulators.

If you can get the prop out of feather, it should windmill enough that the starter is not necessary for a re-start.

Dave

[WebMaster]

I'll bet you were 500 pounds under gross. Not a lot more than that.