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Question for Bob Roller
07/10/18 at 21:23:56
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I was listening to a radio program today about the rising temperatures around the world today and heard a comment that it has gotten so hot in Phoenix, AZ that there are days that aircraft can't take off. Is that a fact? I have jumped from enough aircraft to know that it is a consideration when jumping but never heard of the temps grounding aircraft.

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Tony Smith
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Re: Question for Bob Roller
Reply #1 - 07/11/18 at 02:21:39
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Not intending to jump over the top of any reply Bob might make, but I am a now long inactive commercial pilot and I can answer the question.

The answer is really in two parts
Most modern passenger jet aircraft have such an enormous reserve of power that hot and or high airports are irrelevant to them. Similarly most modern turbo prop aircraft are in a similar situation.

Back in the day (not that I flew them) DC-9s were reviled by the internal airline pilots in Australia that flew them into places like Alice Springs or Mt Isa as on a really hot day they would have to offload freight, fuel and passengers (in that order) to make calculated take-off weight. A little four engined jet commuter and freight aircraft of British manufacture (can't remember the type) had a similar problem in that they were chronically underpowered and if operating near max weight the freight operators in Australia used to fly them at night to get better air density.

As far a GA piston aircraft are concerned the effect of temperature and/or height are legendary. I took off in Western Queensland once in a 6 cylinder Piper and quickly discovered that its real world performance did not match its stated book figures (when it was new 40 years beforehand) and the thing had so little climb performance I lacked the courage to try and turn. Fortunately the country where I took off from was notable by being as flat as a pool table. After an hour or so of flying at around 30ft it burned off enough fuel to gradually creep up to 3 thousand ft at which point I started breathing again.

So, yes, temperature can have a devastating effect on low powered aircraft's ability to take off and climb away.

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Re: Question for Bob Roller
Reply #2 - 07/11/18 at 17:21:26
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The issue was in 1990 I think, I wasn't living here at the time, moved here in Oct., 1993 .
To get to your question, the aircraft performance charts, for V1, rotate and V2 speeds and leading edge and trailing edge high lift device settings .
Engine % rpm targets for and the older generation aircraft that used the EPR  ( Engine Pressure Ratio ) system engine power setting .
These charts topped out at 120 F, the temp here then got to 121- 122 F, 49-50 C., so you could not legally operate the aircraft until the temp came down to 120 F .
To answer your question, the airport was not closed due to heat, just like an airport doesn't close because it's too cold .
Every once in a while you'll hear of the regional jets that airlines use for commuter routes, will be grounded  due to heat, but this is a economic issue, you can carry passengers, but not a full aircraft, or leave fuel off, so they decide not to fly due to it not being financially viable .
Boeing, McDonnell Douglas and Airbus revised their performance charts  to higher temps after that, I think they go to 130 F.,54 C, now .

If you have the Bing manual for carbs, there is a chart in there, for temperature and altitude correction for jet sizes .
On a typical summer day here, which is about 105 F, 41 C., the elevation of Phoenix at the airport is 1130 ft, 415 m, the 'density altitude ' due to elevation and temperature, is around 6,000 ft, 2200 m .

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