KW,

Sporty's Pilot shop has a "slide rule" calculator of the adds/deducts for takeoff/landing performance for various runway conditions: about $25.00.

The % impact of a grass/soft/incline are pretty much the same from one aircraft to the other.

Jgreen

Thanks Jgreen. I just looked it up at Sporty's. It looks like it just might be what I need.

KW

Since I started studying light twin performance, and in particular the Piper Navajo, I noticed that besides no provision for such variables as runway slope, wet, or contaminated runway, Piper includes the accelerate-stop graph only. Beech and Cessna include both the accelerate-stop and accelerate-go graphs. Beech goes further by including one engine inoperative take-off climb gradient graph, making it a simple check.
I wonder if these graphs are used all that much in the GA community, especially on long runways. At work, we use a computer program, where we input all data, and it will compute performance on any runway with given conditions. Makes it easy for us. Has anyone ever heard of such software for piston twins? I hope to get some input on this matter from all those GA pilots out there.



KW

That about sums it up.

Navajos were used extensively in part 135, you would think that the op-specs of some operators required more formal data than 'you are on your own'.

I guess piston twins in GA service don't have regulated departure and arrival performance requirements, and as such, the pilot community is not much into it. In FAR Part 135 service however, as you suspect, it's a different story. This morning, after reading your post, I dug-up a copy of the FAR's. Sure enough, Small Transport Category Airplane performance is regulated. There is a requirement for runway slope calculation, accelerate-stop data and performance capability, accelerate-go data and performance capability, though the accelerate-go requirements for small airplanes differs somewhat than for large airplanes.
So how come there is no such data in the Navajo POH. I suspect that part 135 operators have this additional data in their POH's. I hope someone on this forum does operate a piston twin under 135 regs, and can shed some light on this issue. I will also contact Piper, and inquire about it.



KW

Except the Navajo is not small transport. If it was it would have been certified under Part 25.

From Handbook 8900.1 4-490:

"Small Transport Category Airplanes. A small transport category airplane is an airplane of 12,500 pounds or less MTOW certified in the transport category. While part 25 permits certification of small airplanes in the transport category, manufacturers have rarely chosen this option."

What is the mission you are trying to meet? This is the most complicated approach to flying a Navajo I can imagine. What am I missing?

You are correct. For my projected usage purposes though, the Navajo is a small transport airplane, though technically speaking, as defined by the FAA, as it applies to FAR part 25 aircraft certification, it is not. It is not important to me whether the airplane is certificated under part 25 or 23, though FAR 25 airplane would have higher safety margins. What is important to me is that the airplane has performance safety margin, to the more stringent criteria, as required under part 135 operations, or close to it, although I will operate it under part 91.

KW

Single Engine Performance on a PA-31/350 isn't much.

230'/min (rough numbers at 120KTs that's 100' mile AFTER you get the gear and flaps up)

http://www.risingup.com/planespecs/info ... e372.shtml


For Comparison a B1900D

Will do 670'/min.

http://www.risingup.com/planespecs/info ... e372.shtml

There is no specific mission on my mind, just safe, everyday airplane operation, in vmc or imc, day or night, all weather, just like I do it at work. At work though we have EFB's with performance software that will compute everything in seconds. We just have to input the variables, such as the airport, runway, wind, temp, weight, etc., and it spits out all the data, including engine out routing. In a plane like a Navajo, one has to do it manually, but to do that, we need few graphs. In the standard Navajo POH there is an accelerate-stop distance graph, single-engine rate of climb graph, but there is no accelerate-go distance graph, or single engine climb gradient graph. It's not so complicated. You are not missing anything. Operating under part 91, this performance is not required, unless you want to do it, to guarantee every step of the way.

KW

The normally aspirated Navajo will go up the hill on one engine at about 315 fpm at max gross weight of 6200 lbs. The turbo -310 at 6200 lbs will do about the same. These numbers are out of the respective POH's. Not as good as a 1900D, but not too shabby for a piston powered twin.

KW

The normally aspirated Navajo will go up the hill on one engine at about 315 fpm at max gross weight of 6200 lbs. The turbo -310 at 6200 lbs will do about the same. These numbers are out of the respective POH's. Not as good as a 1900D, but not too shabby for a piston powered twin.

KW

Accelerate - Go in a Navajo? You will be much better served with a few rules of thumb. The numbers generated by test pilots for those charts will not be achieved on a typical GA mission. Performance is all over the board with pistons and varies significantly by airframe and technique.

Fly under gross. Buy a Panther. Life is good....

Yes, accelerate-go for a Navajo. If your engine fails after liftoff, and you calculated the accelerate-go distance for your given weight and existing conditions, you continue single-engine climb, and maneuver for a landing. Everything should be accounted for, nothing left to chance. A proficient pilot will be close to book performance, close enough anyways. Beech and Cessna include the accelerate-go graphs in their POH's. Standard Navajo POH does not. However, I am sure the commuter operators of Navajo's have it. That is what I am looking for now.

KW

That's it, sometimes one has to reduce the take-off weight to guarantee the required engine out climb gradient.

KW