Bruce asked...."are the altitudes listed in the take off and landing distance charts actual altitudes or density altitudes?"
The TO/Landing data is corrected to density altitudes by the temperature columns. To find a standard day (SL/59F) you'd be off by 1-degree...
when you use the SL altitude and the 60F column. All the other columns correct for density. (And just to dot the "i" and cross the "t"....the altitude column is Pressure Altitude. Obtain PA by setting your alitimeter to 29.92 and reading the indicated altitude. Don't forget to reset it back to local baro. press. or field elevation before departure.)
Notice also the comment:
"Performance figures are for zero wind velocity and hard surface level runway. Speeds are true indicated airspeeds."
According only to my faulty memory (from a factory demo pilot's fam. course I once took when I was with British Aerospace).... increase TO
ground-run by10% for 2% uphill gradient and 20% for 3% uphill gradient. Increase TO ground run by 10% for "short, firm turf". (whatever
that means.) So a turf rwy with a 2% uphill gradient would add 20% according to the
planning data that BAe issued us. There were appropriate disclaimers about accuracy.
Uphill gradients were treated as obstacles for purposes of climb. Downhill gradients were not adjusted for any purpose except climb. (TO climb gradient charts were consulted for obstacle clearance. But a caution existed in that obstacle clearance had to be computed from the beginning of TO roll... ...not from end of TO... an important difference that consisted not only of the different gradient but also added another 35' to the height of the obstacle, because TO distance was from brake-release to 35' AGL.)
It was always interesting to me that a headwind could not easily overcome a TO distance limitation...but could an obstacle clearance limitation. I later found out that was because obstacle clearance was based upon climb gradient charts which in turn, were based upon air-distance travelled....not actual distance. (In other words, climb gradient charts were adjusted for wind. This British method may be a variation from U.S.-published methods. I don't know, but there were many such minor differences. I always found the British data more detailed and possibly more accurate than U.S. mfr'r data (which usually just published the most restrictive condition and let any minor advantages go unrecognized.)
I was suspicious of the C-170 published data at first, but I've since realized it's surprisingly accurate for the average condition.
Hope this helped.
). We just purchased 23 acres of wheat field that is relatively flat and will accomodate approx 1750-1800 feet of sod strip. There is a bit of a grade that has not been measured yet and I am eager to see how accomodating it will be for 9CP. Thanks.
