Long range flight with rear engine only

[proto]

Dear Gentlemen

I had a C337P for years in the 80's and then I stepped up to the bigger cessnas and TP.

Recently I aquired a additional aircraft: The '68 T337C for one reason - to fly to Africa. The aircraft is actually in his annual check and will be equipped with a ferry tank.

Here the story: One owner of a similar aircraft told me, that the range can be incresed dramaticaly flying with the rear engine only. It means to feather the front prop and to fly with a speed of some 130 KTAS. That guy did this to fly to Lebanon in the 90's.

Now to my question: I did not find any notice in the manual. On the other side, the proposal make sens, since in level flight one engine can do the job. Has any one the answer ?

Thank you

PROTO

[WebMaster]

It's not legal. OK, you know that. And you probably know that the O-2's were ferried to VietNam, Okland to Hawaii, with big ferry tanks. They flew at reduced power settings, with big ferry tanks, but they flew with both engines. If I remember correctly, big ferry tanks don't require anything special, as long as you are less than 30% over gross. That would be an additional 1300# for your plane. The plane won't get off the ground with one engine at that weight. I think it would not maintain level flight at that weight on one engine.

If your plane has the aux tanks, you won't be able to feed the front engine aux to the rear engine.

Brian Von Herzon has crossed the Atlantic several times in his Super Skyrocket. He has flint wing tip tanks, which provide some additional fuel.

The longest stage, across the atlantic, assuming you are going over the northern route, is about 670 nm. You plane would be able to do that with out any difficulty, without ferry tanks.

MaryAnn, from Riley, said she had a customer with a Super take off from Goose bay with out one engine. Crossing went well, and he apparently flew for a while with only one engine. not to save fuel, only because the engine was broke.

What route are you going to fly?? Brazil to Africa?

[proto]

Hi Larry

thanks for the rapid answer !

Certainly, i can imagine that the procedure 'one-engine-cruise' is maybe not legal. Can be. But we are are looking for max. efficiency. !

In any case, my aux-tank is certified (has his paperwork) - and the weight is in the limits ;-). I know the limits of the skymaster...

You say: ^^ If your plane has the aux tanks, you won't be able to feed the front engine aux to the rear engine.^^

My answer: Right ! But for climb and final approach, i'll consume the aux-tanks. Ah - the skymaster's aux-tanks are famous...

You say : ^^Brian Von Herzon has crossed the Atlantic several times in his Super Skyrocket. He has flint wing tip tanks, which provide some additional fuel. ^^

My answer: The flints are ok, but not in my budget - normally I d'ont use so much fuel, so this modification is not required.

You say: ^^The longest stage, across the atlantic, assuming you are going over the northern route, is about 670 nm. You plane would be able to do that with out any difficulty, without ferry tanks.^^

My answer: The atlantic is one thing - but I fly to south - africa. There are crazy and corrupt people to OVERFLY. I have some experience - so I need a max range of + 1600 nm.


Of coarse, the Skymaster may fly perfectly with one engine - but my question is very simple: IS IT REALLY MUCH MORE ECONOMIC WITH ONE ENGINE FEATHERED ?


Thanks very much.

Proto

PS. Routing is Geneva - Morocco - Senegal - an then ??? depends...

[WebMaster]

In the '60's, I spent some time on that continenent. It isn't any better today.

Since I don't have a T-, you'd would just have to get up to altitude, and watch your fuel burn. Currently, my plane won't fly on the rear engine only. It's out!!! The new one isn't here!! I think my weight and balance is really out of wack right now!!

In theory, of course, it seems that you would get much better mileage with only 1 engine.

[Mitch Taylor]

I'm not sure you can hold altitude on one engine with the ferry tank full. Also, I'd be more concerned about how much harder you're running the rear engine.

[kevin]

I agree with Mitch. Running the Skymaster on one engine will require a lot of power to maintain altitude, and I would worry about what you would be doing to the engine.

Also, on that year aircraft, you cannot burn from the aux for climb. You have to burn from the main for an hour before using the aux. If you don't, you will vent the return flow from the engine (something like 5 gph I think, but I am not sure) overboard.

Run 'em both at 55% power or so. You will get much better efficiency, much easier on the engines. And please look into the fuel system carefully.

Kevin

[SkyKing]

Hey Larry,

Where did you get the notion that "It's not legal" to fly the Skymaster on one engine in cruise, or for that matter, to perform single-engine landings... keeping in mind, of course, that single-engine takeoffs are placarded as a no-no?

Our '77 P-model POH speaks specifically of single-engine operation and single-engine cruise flight.

SkyKing

[SkyKing]

One other thing, even the "Performance - Specifications" on sheet number "ii" in the front of the POH specifies "Certificated Maximum Operating Altitude" as being rated as "Single OR Twin Engine" @ 20,000 feet, although the SE Service Ceiling is 18,700 feet.

Obviously, one of the great redeeming features of the Skymaster with its center-line thrust, is its abillity to fly on a single-engine. Why not take advantage of it, especially on a long-distance flight when time is not a factor?

As far as the Skymaster requiring a lot of power to maintain altitude, or needing to "worry" about what you would be doing to the engine, that would seemingly depend on how the airplane is loaded, and using proper piloting technique with the necessary amount of mixture and cowl flaps to keep things in the green. I just don't see how you'd 'hurt' the engine, all things considered.

SkyKing

[proto]

Thanks for your competent answers, folks. I'll read all that carefully that (misty) weekend.

Greetings from Switzerland

Proto

[Ernie Martin]

GMAs, a Skymaster expert who writes in another Message Board, says that he has data which shows that range is not extended by single-engine operation, when compared to running both engines at the lower power levels (e.g., 2300 RPM, 18 in of Hg) which result in maximum range.

Ernie

[proto]

Hy folks

I calculated the whole thing and I found that the one-engine operation brings you 15% longer range.

Instead 2 engine producing twice 33% PWR, you fly with the rear one with 66% PWR. It works! 22 versus 26 gal !

Actually, we have to replace a wing-boot, so I can't check it in flight, but there are numbers...

With that trick you can fly up to 1500NM with the 128 gal. tanks! Sounds good!?

All is legal - the only problem is that the TBO-time is also running on the feathered engine. This procedure you can apply just for very long ferry-flights with no additional tanks.

Calculate and try !

[kevin]

Try flying it, I think you will find that speeds, fuel flows, etc do not work out as you expect.

Kevin

[proto]

Yeah, i'll try this. I am just woundering that no one did this before here.

Bye

Proto

[kevin]

Many of us have flow Skymasters on one engine.

Speaking only for myself, I really question whether a Skymaster at gross weight will maintain altitude on 66% power on one engine, as your calculations require. It has been a couple of years since I did it, but I remember it requiring more than that.

If it *will* maintain altitude, it will be at or near best rate of climb airspeed, with a high angle of attack. That would be a very uncomfortable way to fly the airplane for long periods, the air flow to the rear engine would be compromised, and it just doesn't make sense to me that a higher angle of attack would be an efficient way to fly the wing.

So that is why I suggested you fly it in a closed course to eliminate wind effects, and see what works the best overall. I think you will find that low power settings on both engines will serve you better.

By the way, 100 knots is the best glide speed with both engines feathered, so your best range should occur by reducing power to maintain that speed. This is about 10 knots faster than the best single engine rate of climb speed.

Lastly, if you are flying over water at cold temperatures, keep in mind that if you cold soak the front engine by flying it shut down at cold outside air temperatures for a while, you will very likely find it difficult to restart if you need it (because the other engine failed).

Kevin

[skymaster]

i think someone should do and report the results. my money is on single engine. could be wrong but never in doubt. JCH