Training

bruce.lynn@me.com

Hi everyone just purchased my first aircraft, a Cherokee 140' 150hp. I'm just a few weeks from taking my checkride and I have some questions about dentistry altitude that my cfi's have never been able to get across to me. (Maybe I'm just a slow learner). I have no problem calculating it I just don't know how to apply it in the real world as far as how to accurately predict how I can safely load my plane at a high density altitude. My plane has a useful load of 900 and has 50 gal tanks. I am in ruidoso nm for the summer and the field elevation is 6300 ft with daytime da's in the 8000 range. Any help would be greatly appreciated

Scott Sherer

Hi and thanks for writing. I don't have your performance charts handy but I'll share this with you. The climb performance of your aircraft at high altitudes is very low, perhaps as low as 100 feet per minute. If you're cruising along at 8,000 ft and you want to climb to 10,000 feet it could take a while. When you're in the air and it takes a while it doesn't matter. However, with a density altitude of 8.000 and poor acceleration and climb performance, you may not make it off the runway before running off the end. Or worse yet, you can't get out of ground effect on the takeoff climb. Many pilots without turbocharged aircraft have met their demise in this situation. Here's how to beat it. 1. Fly in the early morning when in high density altitude situations (hot and high). 2. Don't fly at gross weight. Take yourself and that's it with 1/2 fuel if possible. This will help. Good luck.

bruce.lynn@me.com

Thank you Scott. I've flown it up here like you said..early morning and solo with half fuel and it is quite lethargic. I did actually get close to 250 ft/min climb but I do not like it and have no plans of trying to take anyone with me. I'm only up here for 3 more weeks and then back to my home in Texas. There is over 8,000 ft of runway so it does give some margin there. I just wondered if there was any actual calculation to reduce your load but I'm guessing it's more of a common sense kind of thing? I just joined this site and it's full of great information. Thanks again!!

Scott Sherer

Hi Bruce, most airplane POH's have performance charts for this and other scenarios. If it's not in your POH, you're SOL, LOL! Stay in touch, I'm pleased that you've joined and I'm here for you when you need me.

Brother

Think about two things. Climb performance and the distance you are covering while climbing. Sometimes people only see the positive climb and then they quit. Remember also that once you climb a 1000’ above the airport that you now have a plane that is operating at 9000’ DA.

Distance: if you are climbing at 85-100mph, you are covering about a mile and a half a minute. If you are only getting 100-250 rpm, you have to cover 6 miles to get to 1000’ AGL. Mountains usually have hard pokey bits so you need to make sure you don’t hit one straight on while trying to climb over it.

High and hot: you will be climbing harder for longer, watch your cooling.