marcum@rhino.UUCP (Alan M. Marcum) (06/05/85)
A couple months ago, Jeff Williams (ihnp4!cfiaime) responded to the query >> My question is: is there a correction factor which >> works for different climb speeds? Is climb performance linear with >> speed? with the following: >As a rule of thumb, add one mile of enroute distance for each >1000 feet of climb....This trick works best for cruise climb, and >is accurate to 1 minute or so and 1 or 2 gallons. In preparation for taking a Mooney 231 to San Diego (from the SF area), I called Mooney, and talked with people in the Flight Test Department. We discussed various techniques not described in the Pilot's Operating Handbook (POH), and their effects on climb performance. The climb charts in the POH are for best rate: 40"/2700rpm, full rich, 96KIAS. A modified climb, using Vy power and 105 kts would not decrease climb rate much -- 5-10% or so; the curves are pretty flat. The "normal climb" is at 75% power (33"/2600), full rich, 95-115 kts. The POH has no climb performance data for a normal climb. The Flight Test engineer mentioned that the mixture COULD be leaned, to a bit richer than Best Power -- but the CHT must be closely monitored. Airspeed should be about 105 kts; rate of climb will be about 700 fpm up to critical altitude (~16,000'). Fuel flow will be a bit over flow in cruise at 75% at the specified altitude. (This was all done assuming the plane was loaded to max. certificated weight.) Regarding descent, what follows are rough ballparks. Flight Test indicated that a 3" decrease in MP should result in about 500fpm down at the same airspeed, roughly. (This is assuming a cruise of about 140 KIAS [IAS, not TAS], and that 500fpm down yields about 10 kts.) Fuel flow will decrease about 1.5 gph. As far as cruise, incidentally, the 231 POH provides only one set of speed curves, rather than one for best power and one for best economy. Flight Test said that speeds will be the same, because of a recommended increase of 0.8" MP when going from best power to best economy. Why fly at best power? Cooling, primarily. By the way, I found the people at Mooney Aircraft Company to be very helpful. They had no hard data on much of what I wanted; the folks from Flight Test got out the charts they had, did some interpolating, did some educated guessing, and we came up with some data. What other information do people have for other aircraft that isn't in the POH? -- Alan M. Marcum Fortune Systems, Redwood City, California ...!ihnp4!fortune!rhino!marcum