Gear Retraction on Take Off

[aldoradave]

My 73 P337 has electro hydraulic power pac and which is not driven by any one engine, and seems to be much faster than the older models. If there was "no change" in SOP then there would seem to be little value in the gear door mod. I will PM Ray Torres on his thoughts and post what I find out.

Dave Dillehay

[skymstr02]

The USAF -1 TO (Flight Manual) has the flight data in the performance charts that show the rate of climb on the rear engine with the gear in transit (doors open) at -240fpm. Notice the minus sign in front of the number.
That means that a trained test pilot could not maintain a positive rate of climb on one engine with the landing gear in transit.

[tropical]

Originally Posted by aldoradave

My 73 P337 has electro hydraulic power pac and which is not driven by any one engine, and seems to be much faster than the older models. If there was "no change" in SOP then there would seem to be little value in the gear door mod. I will PM Ray Torres on his thoughts and post what I find out.

Dave Dillehay

The "value" of the gear door mod is fewer moving parts and elimination of the two big gear doors which do cause a bit of drag during retraction.

Essentially I treat the Skymaster like a single engine plane on take off, once I'm high enough for no landing on the runway the gear comes up.

[billsheila]

Essentially I treat the Skymaster like a single engine plane on take off, once I'm high enough for no landing on the runway the gear comes up.[/quote]

I must be mis-understanding you. Why would you treat the Skymaster like a single engine plane on take off? For me the whole point of owning one and carrying around that extra hulk of steel and aluminum is mostly for this phase of flight, ie it is critically important that it will still climb in the event of a loss of a single engine on take off.

Regarding retraction, the data noted above from the O-2 manual suggests you indeed do have a version of a single engine (ie you are descending) if you put the gear in motion on one engine. No such data is quoted in my manual. The airplane is perfectly happy flying along with its legs hanging out and will apparently still maintain a positive rate of climb at Max Gross on one engine in such configuration. So I am confused as to why you would in effect be suggesting you turn your twin into a single by moving the gear handle. Of course once you have some altitude flying an "engine out" single isn't a big deal for 12-15 seconds of retraction time. But as I said, maybe I am just mis-reading your statement above.

[Roger]

I believe the analogy about being like a single engine aircraft is that in certain configurations and scenerios, the Skymaster with one engine out, climbs like a single with one engine out. This would specifically be hot/high or both, on takeoff, one engine out, and the doors in transit. Get it ?

Just this week my gear breaker popped after takeoff, and it was very apparent that it did. Not because some light blinked or horn beeped. But because it was climbing like a wallowing pig with the doors open. I would never like to experience that with an engine out.

I would think this especially so in those aircraft that have the older style single engine driven hydraulic pump, when that engine goes.

[billsheila]

OK, I am a little thick but I get it now. So Tropical and I are in agreement, I think, except he still wants to see the gear in transit ASAP after becoming airborne does he not? So I gather the logic would be get the plane cleaned up ASAP

Roger, re your incident, presumably your breaker wouldn't have popped if the gear were down and locked right? So why not leave them down and don't risk the possible effects of any configuration changes until you gain some altitude...which was my original point.

I checked my manual again and am embarrassed to say it indeed does contain data on the minus 240 ft/minute effect of in-transit climb impact of retraction (on single engine, rear operating) and quotes minus 110 ft/minute (on single engine, front engine operating). What is not quoted is the drag effect of the gear themselves, ie if left down.

Back to your incident, do you think your plane would climb on single engine, other feathered, gear down and locked...or only a cool day?

I like the suggestion of trying this at altitude and figuring it out that way. In the meantime, I will fly a 336 for the first bit of every flight.

[Roger]

Down and Locked is good. Up and locked is good. In transit blows.

Yes the plane should climb with one engine out and the gear down under most scenerios ( ie.. standard day, or not overloaded, etc.. ) Always check your book and CG to be safe just in case.

My scenerio was classic in that I had set my Props and Throttle for cruise climb and was about 450' off the runway (which was sea level by the way) and I put the gear up. I hadn't flown it in about 3 weeks, and for whatever reason, the breaker popped. I knew almost instantly what was happening becuase it almost stopped climbing, looked out at my shaving mirror on the strut fairing, and saw the open door.

Moved my left knee away from the circuit breaker panel and was happy to see the popped breaker . Happy becuase it seemed like a no-brainer. Worse if you have stuck doors and the breaker is in, because at that point your potential for quick fix deteriorates. Popped the breaker back in, and doors closed immed.

I cycled the gear 3 times when at 2000 feet to make sure everything was working, and didn't have any more problems.

Once it happens to you (gear doors stay open) you won't ask the question "why wait" ever again. Sure you don't look like a fighter pilot, but it's worth the perceived humiliation

[tropical]

Originally Posted by Roger

I believe the analogy about being like a single engine aircraft is that in certain configurations and scenerios, the Skymaster with one engine out, climbs like a single with one engine out. This would specifically be hot/high or both, on takeoff, one engine out, and the doors in transit. Get it ?

Just this week my gear breaker popped after takeoff, and it was very apparent that it did. Not because some light blinked or horn beeped. But because it was climbing like a wallowing pig with the doors open. I would never like to experience that with an engine out.

I would think this especially so in those aircraft that have the older style single engine driven hydraulic pump, when that engine goes.

Your analogy is correct.

[JeffAxel]

My POH for a '77 T337G says the penalty for gear down amd locked, doors closed is the loss of 110fpm climb on one engine. The plane will climb on either engine with the gear down amd locked with the doors closed. It will just maintain altitude with the gear in transit if everything goes right. The aforementioned -240fpm is what my POH says as well as the penalty for gear in transit. I am sure loosing the big main gear doors helps some as far as drag goes, does any of the paperwork that comes with the STC say what the difference is?? That would be useful information.

[Ernie Martin]

Two thoughts.

1. I don't think any of us should assume the POH climb rates to be realistic for our aircraft. Those numbers, squeezed to the max by Cessna, are for brand new aircraft, with perfectly smooth (and waxed) skin, perfectly tuned engines, perfect-pitch props, etc. Ours don't fly that good. I assume 100 - 200 fpm penalty for age, plus the adjustments for temperature, pressure density, etc., and I try to fly below max load, so if an engine fails I can get close to the POH numbers.

2. Of the added drag introduced by the gear in transit, I don't know the proportion of the big doors (the ones removed by the STC), but if you've seen a gear retraction test up close, you know it's big. My guess 2/3 of the in-transit added drag is due to the big doors.

Ernie

[hharney]

Originally Posted by JeffAxel

I am sure loosing the big main gear doors helps some as far as drag goes, does any of the paperwork that comes with the STC say what the difference is?? That would be useful information.

RT Areospace did not provide any new numbers for the gear door removal......fly it by the book!