Density altitude and take off distances

Just for fun, take off in a PA-28-140 at a density altitude of 3000'

@1950 gross wt. ~1100' @ 2150 gross wt ~1200' ground run

over a 50' obstacle at 3000' density-altitude in a PA-140 is 2125' @ 1950 gross wt, closer to 2450' @ 2150 gross wt.

 

My pleasure. I've a soft spot in my heart for the 140. It gave me my first airplane ride, thanks to a father who wanted to go flying and a mother who wasn't told what her boys were up to. (It was all down hill from there)

 

Just remember in addition to considering that the book numbers are for a standard day, that you engine may have old grey mares in place of the horses.

Planeflyr

 

What is all this stuff about altitude density. I never found it to be dense. It has always been rather thin if I remember correctly. Now, the older I get the thinner I get and I just don't know what the dense stuff is.....unless maybe it has something to do with the altitude of my head. Or maybe there is some dense stuff at that altitude. Or maybe I just don't want to think about stuff that is over my head. Never been able to figure out that stuff anyway because I don't get it.
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That whole density altitude thing is just a fancy ground-school, book-learnin' way to explain the plane tellin' you that you're too dumb (dense) to go flyin' that day. And that you should lay off the desserts.

 

Heck ! That take off stuff is easy to figure out. You gotta make sure that there's plenty of gas to take off but not so much to go anywhere so you're not too heavy. Then make sure the runway is real long so that when you get two feet of altitude you can ride along on that cushion of air until some gas burns off and then you climb.....sometimes. If it doesn't want to. just shut her off and land. REMEMBER ! I said make sure you have a long runway.
The equipment that I flew always had a density/ altitude problem even on cold days with just the pilot on board. It is really hard to push forward on the stick when you are supposed to be pulling back for a slight climb. High PF.
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My mother was a bit different than most. She encouraged most of the things that my brother and I attempted to do. My brother swam the rapids on the Potomac at Great Falls and he and his buddy took great joy in following the current through a rock that had a hole in it. Three feet in diameter is wide enough for your body if you are on target. She never restricted what I thought that I could do but there were times when she should have...but I never told her that. All she ever said was, " Be a good boy and be careful."
Some people have told me that she was really trying to get rid of me. Didn't work.
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OK - if you want primitive DA explanation, here's my procedure.

Walk off the distance in the turn row from the start of the takeoff run to the fence (no higher than 3 ft.) on the other end.

Pace back 3/4 of the distance and put a sharp stick in the ground (no higher than the wing please).

Fire that puppy up and head for the fence - if you don't have 50 % of Vx by the time you get to the stick, power off, turn around and go home - or try again. (No math or DA calculations involved)

If no cigar, come back in the morning when it's cooler (hence the DA story).

NB: Ignore the above and face having to explain the barbed wired on the gear struts or worse.

 

Good, Roy, I'll try that some day if I ever get in an airplane again. It's all good stuff and those new pilots have to pay attention to it. Luckily, I have been able to feel what the airplane was doing in time to prevent an embarassment but then I wasn't flying any of the newer or heavier stuff in the hot high regions.
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Disclaimer - Don't try this at home boys and girls. If you have never taken an airplane off from a turn row, the beach and a dirt road - don't start now. I was just trying to demonstrate a slightly more "academic" approach to "seat of the pants flying" - still with historical applications.

For those of you just now learning to fly, with instructor aboard, set the power at 65-75% with the brakes locked, and then try a takeoff on a long-long-long runway. That will give you all the experience you need to disabuse you of the idea of trying something foolish in a hot-high environment.

 

Roy,you brought back a stupid thing that I did when I was young and dumb. I tried a take off in a Stearman at cruise power from the intersection of the runways. Of course, I ran out of runway, altitude, and had an engine problem all at the same time. Discovered the engine problem too late and faced a row of tall pine trees before adequate airspeed was attained. A staggering turn at just above stall speed allowed me to change direction and fly parallel to the trees only to face some power lines ahead. Somehow we managed to jump the wires and settle down on the other side over an orange grove where the airspeed increased enough to climb a little bit and get out of trouble....until I landed and faced the airport manager and a couple of instructors. You have no idea of the full meaning of the words. " REAMING OUT".
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