Climb Rates When Hot and High

Discussion in 'Hangar Flying' started by fly2kads, Jun 18, 2011.

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  1. Jun 18, 2011 #1

    fly2kads

    fly2kads

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    It has been unseasonably hot here in the Dallas/Fort Worth area lately (103 F yesterday), so my sun-addled brain has been contemplating destiny altitude and it's impact on performance. (My sun-addled brain has also been contemplating cold beer, which may or may not improve my thinking.) We are not exactly high here, with elevations running 550-650 ft MSL, so density altitudes are only topping out around 4000 ft.

    What I would like to know, from people who are flying in places where density altitude is more of a factor, is what climb rates or gradients do you find minimally acceptable? In reading the LSA spec (ASTM F 2245), it calls for minimums of 312 fpm at Vy and a gradient of 1/12 at Vx. Will that work where you are? I know this will be somewhat dependent upon the surrounding terrain, such as whether or not you are going to have to climb over a mountain pass after departure. So let's hear it…what are YOUR minimums when things get hot, and what is driving your choice?
     
  2. Jun 20, 2011 #2

    PTAirco

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    Anything less than 300fpm and I'm waiting for a cooler day. I was in Palm Springs today in a well maintained 150. One lightweight passenger, 3/4 fuel and it was HOT, probably about 100F and climb from 100ft to 6000ft took forever. But it got there eventually and as long as you can work around terrain, I can live with that on occasion.

    You can never have too much power.
     
  3. Jun 20, 2011 #3

    PuertoRicoFlyer

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    The density altitude here in Houston was 3,010ft even though the airport I fly out of (9X1) is only at 122ft. Talk about big difference in performance during takeoff! Yes it was VERY HOT (102F) today. :cool:
     
  4. Jun 20, 2011 #4

    teknosmurf

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    It is starting to hit that time of year around here were 105 to 110 is common. Most airports around here are in the 1000' to 1500' altitude range. It's not uncommon for DA to be 4000 to 5000'.
     
  5. Jun 20, 2011 #5

    Topaz

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    We're in the same boat at Skylark (CA89). Listed airport altitude is 1,250'MSL. Summertime temps commonly top 110°F (although perhaps not this unseasonably cool year), giving us a density altitude pushing 5,000'MSL.

    Get down to about 400FPM after takeoff and I start getting twitchy. We have a lot of mountains and hills nearby, lots of power lines, and lots of houses containing people who like to complain about airplane noise. There's one development near the usual IP that we have to avoid entering downwind because they say the gliders are "too loud".
     
  6. Jun 21, 2011 #6

    bifft

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    You flatlanders have it easy. Here in the mountains, the airports in the valleys are at 4500' or so, a hot summer afternoon can push the DA to 9000. Runways are long. I have aborted a cross country flight when we were 20 miles from the airport and had only climbed to 6000' (at best rate of climb the whole way (about a 1/70 angle)).
    It is better to start cross countries (where you need to cross mountains) in the mornings, but I have fooled around in the pattern on hot days. Sometimes don't make it to pattern altitude before it is time to turn base.
     
  7. Jun 21, 2011 #7

    bmcj

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    I flew out of KAFF in the early 70's. Altitude was over 6500' and runway length was 4500' with an alternate runway (mostly for glider ops) of 3500'. Never noticed too much problem with climb... I guess you get accustomed to it.
     
  8. Jun 21, 2011 #8

    PTAirco

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    Minimum acceptable climb rate = 65hp Champ with two big guys and full fuel on a warm day.


    It makes one wonder why aircraft engines aren't turbocharged as a matter of course nowadays.
     
  9. Jun 21, 2011 #9

    bmcj

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    I had to fly a 7FC Tri-Champ (terrible plane with that nose gear hanging out there) from the San Joaquin Valley to Riverside on a hot day with two aboard. I couldn't get enough altitude to fly through the Grapevine (mountain pass). Fortunately, there was a high pressure system pushing air south through the pass, so I was able to fly at the mountain face and pick up enough ridge lift to carry us up and over.

    Bruce :)

    NEVER PUT A NOSEWHEEL ON A CHAMP!!!
     
  10. Jun 21, 2011 #10

    Topaz

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    :gig: Ahhh, Bruce. You make me smile.
     
  11. Jun 22, 2011 #11

    PTAirco

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    On Sunday, flying in the desert with winds howling through the Banning pass, it was easy getting some ridge lift as you climb over the hills bordering Joshua Tree park. My passenger was filming and I pointed at the VSI which went from 300fpm to over 1000fpm! In a 150! Nice when you can get it.
     
  12. Jun 22, 2011 #12

    fly2kads

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    Thanks for chiming in, guys. As I mentioned, I live in an area where the density altitudes are commonly 3400' to 4000'. I used to live in areas where the density altitude would reach 8000' to 9000', but I wasn't a pilot then and didn't get to experience what that was like. I am doing some what-if analysis of a relatively low powered aircraft design, and was wanting to check the 'reasonableness' of my results. My calculations are showing a climb rate of about 400 fpm at 9000' and I'm trying to decide if I could live with that.
     
  13. Jun 22, 2011 #13

    Dana

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    What's an acceptable climb rate also depends on the aircraft's speed. On a slow aircraft like an ultralight a climb rate of 250 fpm might be acceptable as the climb angle is still reasonable.

    -Dana

    And they shall beat their swords into plowshares, for if you hit a man with a plowshare, he'll know he's been hit!
     
  14. Jun 22, 2011 #14

    bmcj

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    In the land of Dallas where you live, Cumulo-granite takes the form of low lying scud instead of towering cu's, so as long as you have enough climb to get you safely off the ground and clear of ground-bound obstacles, you should be fine. To answer your question on where we set our limits, I draw my limits from runway requirements, whether the plane I am flying has difficulty with engine cooling during extended climbs, and whether I anticipate climbing high enough to be in cooler air where the cockpit temperature becomes tolerable.

    Bruce :)
     
  15. Jun 22, 2011 #15

    autoreply

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    Like Dana said; climb angle (at a safe speed) is much more important as absolute climb when flying in the mountains. Downdrafts can easily be 1000 fpm and few planes can climb through that, so unless you have 1500+ fpm, it's the angle that will be your most significant constraint.
    I've done a launch where climb didn't exceed 120 fpm on a hot day. No problem whatsoever, you just have to be patient. Very patient.
     

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