Single engine TO
 

Jose's list highlights a question I have had. The single engine rate of climb for the Skymaster under standard conditions varies depending upon the operative engine, the specific model and the publication one reads but would appear to be somewhere between roughly 325 - 375 fpm. I've read though of a number of accidents in which the principle or contributing cause is listed as engine out on takeoff.

Now 300 fpm isn't great but ought to be adequate in good weather and without substantial obstacles at reasonabe density altitude (query "reasonable"). For example I once took off in a C152 at DA approx. 1000 ft. with me (195 lbs at the time), my instructor (approx. 170 lbs) and as I recall, about 20 gals of fuel. Weather was clear but with a near 90 degree crosswind at about 9 (the favored rwy was not available). I noticed that it seemed to take longer than usual to attain rotation velocity and when I did, the plane just did not want to climb. I nearly stalled it immediately off the deck. I pushed it back over, stayed in ground effect and was able to gain enough speed to climb at about 200 fpm which was enough to allow me to turn clear of hills and trees about 1 mile or so ahead. I never quite gained pattern altitude but remained in the pattern and returned safely. Turns out the carb heat was stuck on even though the switch was in the off position and I was not able to get more than about 2250 rpm. Point is, 200 fpm was adequate under those conditions.

I'm assuming therefore that the engine out on TO Skymaster accidents must have occured in poor weather or at high density altitude or have some other contributing factor(s).

Anyone have any insight on that?

Hugh

Hugh:

The 300 FPM SE climb rate is achieved at Vyse, and more importantly, with a "clean" airframe. With the gear down, you loose at least 100 FPM. If the gear doors are in transit, or stuck open, you will do well to maintain altitude. And if you inadvertantly take off with the rear engine not running, and therefor do not have the prop feathered, the increased drag from the windmilling prop will most definitely cause you to loose climb permormance.

By the way, except for the drag of the gear doors, all of these factors are the same for other light twins. Of course with the other twins, you also have the problem of assymetrical thrust to contend with as well.

Mark

That answers it I think. Makes more sense now. I didn't realize the SE rate of climb was quoted in the clean configuration. I was assuming that it was with gear still dowm and I hadn't considered the undfeaethered prop. Thanks.

Hugh

Just to clarify, in case anybody else misreads Mark's post, as I did at first, when Mark says you "lose 100 FPM" he means "your climb rate is reduced by 100 FPM". So if you had 375 FPM with the gear up, it would be 275 FPM with the gear down.

I have experimented some with this, and I am not sure the penalty for having the gear remain down is as high as 100 FPM, but there is some penalty. The airplane does climb amazingly well with the gear down though. I experimented with this to determine if, during a best angle, short field departure, I was better off raising the gear, or leaving it down until I had cleared the obstacles. I decided that I was better off leaving the gear down and continuing to climb at 75 MPH (RSTOL) until the obstacles are cleared, then pushing the nose over and raising the gear when I got a bit more speed. If I remember right, this is the Robertson recommended procedure as well.

On the other hand, I am even more pessimistic than Mark about gear doors stuck in transit. I would be very suprised if an airplane with the gear doors stuck in transit (and an engine out) would maintain level flight. My copy of the O-2 flight manual says that the doors extract a 240 FPM climb penalty during transit, at least after a rear engine failure. If you take the performance numbers from a '67 337, the best single engine rate of climb, rear engine feathered, is 335 FPM at sea level on a standard day. I suspect real world performance is 100 FPM less than that, meaning that having the doors stuck open would result in a gradual descent.

This leads to my strong belief that Skymasters built before 1973 which have the hydraulic pump on one engine and have not had the gear door removable mod done should be flown with the gear down during takeoff until a comfortable altitude is reached, maybe 800' or so. Why? If the "wrong" engine (the one with the pump) fails at exactly the wrong time during the gear retraction, I would not want to be trying to hand pump the gear to finish the retraction cycle at the same time I was feathering an engine and dealing with the rest of the emergency. I know, supposedly if you leave the engine unfeathered until the gear comes up the rest of the way, you can deal with it that way. But that would induce a real "sinking feeling" as well, with the prop windmilling and the gear slowly retracting. And I am not completely convinced that the prop would keep windmilling, depending on the situation and the type of engine failure...

Post '72 Skymasters should use positive rate, gear up in my opinion. With the electric hydralic pump, the gear will continue to retract no matter which engine fails.

My opinion only, each pilot should look at the data and make his own decision. Cessna's recommendation is to retract the gear immediately (positive rate, gear up) on all models of 337.

Kevin

Hugh,

The single engine rate of climb is one factor, but how much runway will a single engine takeoff require? How about to clear a 50 foot obstacle? There's no specs on this. That may in fact be where the danger lies.

Kevin M.,

That's right. Short field with a long TO roll would be trouble as would low rate of climb and nearby obstacles. During my 200 fpm climb I recounted I was staring at nothing but hills and trees for a while. I was struggling to gain altitude and speed so I didn't want to turn too soon. I started about a 20 degree turn at about 400' agl maintaining about 65 kias and it worked out OK. In retrospect though I probably had plenty of room to get up to 800' agl before I turned. But those hillsides looked pretty imposing at the time.

Kevin webmaster,

When you say "post '73" is that inclusive of '73 or truely post '73 only?



hugh

You're right Hugh, I should have written "post '72". I mean 73 and later.

Kevin

No Doors Kit/RSTOL improves engine out
 

Our '77 P337 has the RT Aerospace 'No Doors' deletion kit... this coupled with the improved takeoff/climb performance with the full Robertson STOL kit is the way to go. There's no penalty for the clam shell doors, as they are removed from the equation.

SkyKing

1967 337B

My rule of thumb is not to touch the gear until I reach 500 Feet AGL

Frank

Gear Doors
 

If you are single engine, and operate the gear, opening the doors, you will experience a negative rate of climb. On one accident, as I remember it, the pilot cycled the gear shortly after takeoff, and the resulting negative rate of climb caused the accident. I think, have to look, that it is not just diminished by 250 FPM, that it is actually -250 FPM, for the 10-12 seconds to cycle.
Also, take note, that in 69, it was possible to get gear pumps on both engines. Mine has that, as does Jenny Stack's plane. It doesn't make anything work faster, just gives you the ability to cycle the gear with either engine running.
Of course, taking off with one engine not working is always a root cause. Another thought, however, is that these are reported accidents, and I know that in the Cessna ads of the time, they did get one off the ground with one engine feathered.

Which brings up an interesting point. If you can't get the engine started, how can you feather it?

Single Engine Climb
 

I have a 337H model with main gear doors removed. Three years ago while flying with my flight instructor. He pulled my front engine to idle on take off at 300 feet AGL. I had just raised gear, still had 1/3 flaps down. I quickly dropped the nose to maintain 90 kts. It was a 80 degree day & the airport was 600 feet above sea level. I had 100 gal of fuel on board. My son-inlaw in the back seat who weighs 165 pounds, I weigh 170 pounds & my flight instructor weighs 265 pounds. I made a slow turn to the left to go down wind and could not gain a inch of altitude until I was mid field. Than it started to climb slowly. I managed to gain 90 feet before turning base. I know the front engine was creating drag at idle. If it was a real engine out I would have feathered the prop on dead engine. I was impressed with performance under the conditions of high tempature and high payload. Try that in a single engine aircraft.

gear door mod
 

I rather doubt the gear doors contribute much drag other than during transition. It certainly will not assist in climb other than the weight reduction.

If it were an important as one is led to believe then why did Cessna put them on in the first place?

Since there is superficial drag with the wheels down why not transition the gear at during cruise transition at 1k ft?

You can reduce drag by obtaining a wing removal kit ;>)

Bob

:D

rotation speed
 

Dale, for the very reason you describe is why I do not rotate until blue line is achieved. I fly P337G and blue line is 100 MPH, Loss an engine and keep on trucking. I believe Bob Cook also rotates at blue line. Am I correct Bob?
Jerry:D

Jerry:

Why rotate at 100 MPH? Let me play devil's advocate for a moment on an approach which may accomplish what you're trying to achieve, but (I think) earlier and safer.

In my normally aspirated 337G I rotate around 80 MPH. I then remain at 20-30 ft altitude or so, within ground effect, until I reach blue line of 100 MPH. I do a quick check of engine gauges just before getting to 100 and at 100 I start my climb.

My objective is to minimize rolling friction from the tires. I believe I get to the 100 MPH point earlier in the runway than if I had been rolling through the last 20 MPH of increased speed. Thus, when I hit 100 MPH I've got more runway left, than if I had rolled all the way to 100 MPH. Also, notice I'm airborne at 80 MPH, so if there's a problem with controls, I'd rather find out at 80 than at 100.

In short, I agree completely with getting to blue line quickly, to protect against an engine failure. Why not do it really quick?

Just food for thought and perhaps the start of a healthy debate.

Ernie

Ernie:

I too rotate at 80. Why make those little wheels rotate any faster than they already are? The aircraft accelerates so quickly that I don't think there is any reason to keep it on the ground until reaching blue line.

After takeoff, I climb at 120 mph (top of the white arc) until 400-500 AGL. I raise the gear and retract the flaps, then I reduce power to 75% (top of the green arcs for MP and RPM), and continue climbing at 130 mph. This airspeed allows me to see over the nose, keeps the engines cool, and gives me 500 to 750 fpm climb. The extra margin above blue line also gives me some time to react to any problems and still make sure I stay ahead of the power curve.

Mark

Blue line
 

I have a H model and airspeed is in knots. My blue line is 90 knots
and that is what I climb at or above. I fly out of a short field 1995
feet long to be exact. I rotate at 80 knots level to 90 knots to clear tree line. After that I climb to altitude at 120 knots to keep engines running cool. I was at 90 knots when instructor pulled front engine to idle. Thats going by my flight manual. Best rate of climb single engine, 90 knots. If you read my posting that is what I did. I left the 1/3 flaps in to give me more lift.

climbout
 

Thanks Dale, I now have better understanding of what you did. I do however question the wisdom of your instructor to pull an engine after rotation on a 1900 + foot runway. Yes! I know, engine failure doesn't care how long the runway is, but as described, much to macho for me. It will make more sense to me to practice engine out failure on a more suitable field. On a 1900 foot runway with trees ahead, one other slipup and you have a real crisis on your hands. Like to hear from some of you instructors on this point.
Jerry

In my '73 P337, I fly as taught at Recurrent Training Center. I rotate at 80 mph, and put the gear up when I have a good positive rate of climb (which is always above 102 mph blue line). I'd say this happens at about 200', although I've never looked closely at the altimeter.

In case of engine failure, except in the case of a VERY long runway, RTC's procedures (which are Cessna approved) are that if the gear is down, land, even if there is not enough runway ahead. If the gear is in transit, or up, then go. My normal climb speed is 130 mph unless best rate (110) is needed for some reason.

Obviously, this has to be tempered with the reality of how much runway you have left. If my gear is still down, obstacles are very low, and there is almost no runway left, I might go. But according to their training, this is what often kills people. It is better to run off the end of the runway (on the ground) and hit an obstacle at 40 mph than it is to hit in the air at 100.

When and if this eventually happens to me, will have the discipline to pull the throttle back on the good engine and land, knowing that it will be a crash? I hope so. But I hope more that I am not faced with this choice...

As for truly short fields, all this goes out the window. I have RSTOL, and for a truly short field, I rotate at 60 mph and climb at 75 mph, with gear down and flaps at 2/3, until the obstacles are cleared, at which point I start adding airspeed, milk off the flaps to 1/3, raise the gear, and then get rid of the last 1/3 of flaps. An engine failure during the early part of this procedure is very definitely a crash straight ahead event, just like a single, and is part of the risk I take when operating out of short fields (not often).

I sometimes use the RSTOL procedure in moderate length fields (say 3000') if there are lots of obstacles ahead, preferring to get as high as possible as fast as possible, rather than follow the normal procedure and buzz the obstacles at a higher speed. I am not sure this is the right choice. An example of a field where I use this procedure is Nelson BC, if anyone has been there.

I will be interested to hear your comments.

Kevin

Flaps
 

I read with interest about 2/3 flaps for takeoff. I always use 1/3, and only 1/3, for takeoff. Is it the RSTOL that permits takeoffs with 2/3 flap?
Mine is normally aspirated, so not the same as the turbo models, but POH says 1/3 for all takeoffs. Even at Newmans, 2500 ft grass, I use 1/3.
For GRR, 5000 & 10000 ft paved, I lift nose at 60 (MPH), rotate at 80, level for 100, then gear and flaps up after 500 ft, then engine back to 25 and 25. Climb out at 120.
Is there an advantage to 2/3 flaps? Maybe I have to go read the short/soft field procedures again?
I have to say, I never use 2/3 flaps, because I go from 1/3 to full on final, and from 1/3 to none on take-off.
Thanks for your interesting comments, have to go read some more.

I use 1/3 flaps for normal takeoffs, and 2/3 for landing. 2/3 flaps for takeoff is an RSTOL thing, not applicable to non-RSTOL aircraft.

Kevin

I recently read through Sky Smith's book on "How to Buy a Used Skymaster." I note that over the production lifespan of our favorite plane that the gross weight generally increased as the single engine rate of climb in FPM declined.

Now, I hate to expose my ignorance yet again but...did Cessna make design modifications in the airframe or control surfaces that resulted in these changes or is it simply a mater of how they were recorded/calculated? In other words, did they just take empirical data regarding weight vs. rate of climb and quote them at different points on the curve each year or did they actually modify the aircraft? The engines seem not to have changed so I am assuming it would have been the airframe.

This is an important distinction to a novice shopper. If the different models are structurally identical and differences in climb performance data are really just a matter of how the aircraft was tested, well then that eliminates a significant variable in the selection process. Among my many interests in the Skymaster is safety in an engine out on take off situation. A greater rate of climb in an engine out situation would be a significant plus in my considerations. But if SE performance is calculation dependent and not model dependent, well then I have many more options.

What say the well informed?

Hugh

Hugh:

Planes are like people...they get heavier as they get older. As the model line evolved, the aircraft had options and features added. As you noted, the engines stayed the same, except for the addition of turbocharging. More weight with the same horsepower equals less performance.

I was always under the impression that the airframe and controls stayed the same thoughout the model line, except for changes needed for the P models. But I don't know that for a fact.

Mark

For me, the two critical factors are the gear doors IN TRANSIT and the FEATHERING of the inoperative prop. My '67 has hydraulic pumps on both engines, so it was an option at least then (the buyer had to order it, though).

I had the rear engine quit once on short final. Time I realized what had happened I limped to the end of the runway with the front engine at full power. I started asking some questions and the input I got from all here was that an unfeathered prop would create real drag. I believe it!

It could be easy for us to get complacent about the I-V-F mantra, but due to the critical need feather a dying engine's prop, I've taken to trying to ingrain that into my thinking on all take-offs.

Paul,

Was there time for you to feather the prop in that incident or did you make the runway before you could feather it?

Hugh

Sorry, Paul, what's I-V-F?

Ernie

I-V-F = Identify (the dead engine) Verify (the dead engine) Feather (the dead engine)

Hadn't heard it referred to by the initials. Always seemed critical to me that the pilot NOT panic and feather the wrong engine. There is time to do it carefully.

Ernie

Ernie:

Yes, but it is amazing how often the pilot inadvertantly shuts the the one remaining good engine. And of course, with our CLT, the old "dead foot dead engine" routine doesn't work.

Mark