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VFR flying during extremely hot weather

Like everyone I have been checking the weather and bit concerned for planning the flight tomorrow to LKCS

I could start early morning to avoid the extreme heat but I will be coming back in the afternoon during the extreme hot conditions on the ground. I expect the PA around 4000’ but this shouldn’t be a problem during take-off or landing. I’d be traveling alone and hope to avoid the thermal turbulence by climbing at FL090. Also, I read somewhere that it’D be a good idea to lean the engine rather on the rich side.

What else to keep in mind?
Or just cancel the plan and wait for for a better weather?

Günzburg EDMG

Arun wrote:

Also, I read somewhere that it’D be a good idea to lean the engine rather on the rich side

Leaning the engine “a bit” on the rich side is not a good idea – that’s where the stress on the engine is the highest. Even if that’s not likely in itself to be a big problem with a moderately powered engine (say a 160 or 180 hp normally aspirated Lycoming) it would defeat the purpose of keeping temperatures down.

If you are worried about CHT and don’t have a temperature gauge then I suggest you don’t lean further than the point where you get maximum rpm / manifold pressure – or possibly less.

My experience from flying a 180 hp Lycoming powered C172S is that at temperatures of ISA+10, it is difficult to keep CHT’s below the recommended max 400°F in a long climb. You can’t fly much faster than Vy either, because then climb performance suffers markedly in high temperatures. Right now we’re seeing even higher temperatures than ISA+10.

Last Edited by Airborne_Again at 25 Jul 12:05
ESKC (Uppsala/Sundbro), Sweden

Don’t forget the use of carb heat where needed as carb ice can still form above 30C:

Last Edited by James_Chan at 25 Jul 12:36

Not much to worry about just your(+pax) comfort, low performance and solar cream

I don’t stay too late for the air to cool down if it is humid+hot day (tough not sure where moisture come up in Germany continental weather), I am better to get back bounced in thermals than in thunderstorms

ESSEX, United Kingdom

My recommendation on hot days in light aircraft is to launch early and finish flying by 11 AM.

I’ve been flying in Italy and Spain this week. Temps do get high quickly… Also for the first time I’ve experienced what I believe to be vapour lock on start up. Very unpleasant to have to shutdown, wait and do it all over again while it’s 38 deg outside and probably 45+ inside the plane!


Apart from lower engine performance than usual, overheating, turbulence, and risk of +TSRA, what else are the risks of flying on very hot days? (And I do know that the foregoing can be serious. I just want to appreciate the full catalogue of risks.)

Flying a TB20 out of EGTR
Elstree (EGTR), United Kingdom

OK, slightly tongue in cheek, and a different kind of risk, and perhaps it belongs in another thread :-) but:

Returning to White Waltham a few weeks ago on a hot sunny afternoon with clouds and light wind, at 2200 ft with the LTMA above me at 2500, I swear the throttle was moving between 1600 and 2400 to maintain height and speed.

It was definitely related to flying under a cloud or not – or perhaps more precisely flying over hotter ground or cool, because the clouds weren’t moving very fast.

Booker EGTB, White Waltham EGLM

The hottest temp I’ve ever flown was just above 50C (on the rwy sensor) taking off from Seville (LEZL) in a C172. Made the takeoff roll feel like I was flying a fully laden 747……

In general, engine performance is the most critical factor, which, in turn, determines t/o and climb performance. I’ve had some flights in Africa where we needed to get out below a certain temp, as the (gravel/sand) rwy would otherwise have been too short. So, on extremely hot days and short rwy, do your t/o calcs and build in a safety margin. You may also have to lean for best power even on lowland airports, although the temps have to be pretty extreme for that.

A good rule of thumb is: DA increases by 1000ft for every 8C above ISA.

The performance issue is density altitude as it relates to aircraft and engine performance (i.e. not just engine performance). A turbo solves one problem, but not the other.

It may be stating the obvious but it’s the combination of hot weather turbulence/thermic activity and density altitude that gets you. When a plane is climbing at 300 fpm it doesn’t take a lot of yawing through bumps plus sink to cause a performance problem, especially with low wing loading. Add a hot, uncomfortable pilot, airsick passenger and the aircraft getting uncoordinated and the pilot can also more easily lose control near the ground in addition to performance issues. He may also have issues with leaning for best power as a distraction – at high DA my plane needs attention to that on the upwind, not just before takeoff.

It adds up. My observation only, depends a lot on type – sailplanes for example are designed specifically to deal with it and don’t have engine issues.

Last Edited by Silvaire at 25 Jul 17:51
22 Posts
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