Hot weather/crap performance
 

It amazes me how much performance is degraded now the hot weather (23c today) is here, you get used to takeoff points, climb out rate and landing distance at your home field then along comes a scorcher of a day with no wind and all of a sudden your thinking " WTF have I lost a mag or left the brakes on" or when landing, I always make every landing a short field, but short final ground speed is noticeably faster and roll out would not win me any prizes at the Alaska STOL contest.

Never thought I was say this but roll on the cold, crisp, clear sub zero winter weather.

Yes. Sunny beaches and (sub-)tropical temperatures may look nice when being flown to them - for actually flying i.e. piloting an aircraft the criteria are quite different. I did my most beautiful flight (still a student, flying under tuition then) in February, the runway covered in two or three inches of snow.

The one type of weather one doesn't want for either, though, is what we are getting right now - low clouds and plenty of rain falling out of them. and lots of wind too. Bah, they used to call this summer...

Hot weather/crap performance
 

23C is hot?

It is where piperboy84 flies :eek:

If it gets any warmer he might take off his simmet :D

Had to look up that simmet thing, ETOPS. Thanks - my horizon has been expanded :)

I really look forward to the cooler months here in Oz, at least from a flying perspective. Just being able to fly in 23C (and below) rather than 35-40C makes a nice change. From a density altitude point of view we're not usually as badly off as folks in parts of the US, where high terrain and high temperatures really conspire against you and your aeroplane.

Nearly all my pleasure flying in summer is done in the early morning, before it gets too hot and the atmosphere starts to get lumpy. Might as well be in the office (or preferably at the beach) then.

Or replace it during the hotter "weeks" with a Rab C.
https://www.google.co.uk/#q=rab+c+ne...2F%3B228%3B284

I've noticed this too. Our temps have gone from -30 in the winter to + 30 in the summer. The rate of climb I'm getting from the poor little R model 172 is horrible at the moment.

We are at 250ft above Sea level but already I've seen density altitudes of 1800ft

I'd just about got my forced approaches nailed but now I feel like I'm back to square one with the altered glide characteristics in the hot air, with all the thermals and updrafts to contend with :(

I'm off to spend an entire flight this afternoon trying to nail those forced approaches. At the moment they are pretty much all that is keeping me from my flight test.

You should try a worn out Cherokee out of Albuquerque at 35c. It nearly becomes a single seat aircraft.

Or a 172 from Tinson Pen, four up ... used most of the runway(!) and then took forever to just about manage to stagger up to 3,000'.

I thought the trees at Kingsmuir grew an extra four feet on hot days.

A typical winters day in Johannesburg

Air temperature 26.1C
Dewpoint temperature -4.2C
QNH 1023
Field elevation 5327ft
Density altitude 7514ft

Summer is more interesting with temps in excess of 30C

What VH-UFO and others have said. 23C is nowhere near hot!

I guess the reason I keep visiting this forum is that it is often good for a laugh :)

However there is a valuable message in all of this. High density altitude can be a killer if you don't do your sums. That was drummed into me when I did my PPL theory in Australia.

This may not be a real density altitude problem compared to the tropics but when we up this far norf are used to temperatures in single figures we can notice a difference on a "scorching hot" day. But, good laugh to you guys that fly from 5000ft strips! Can't do smilies on this thing!

To our antipodean friends: it's well known that British centigrade is hotter then Oz centigrade.

Never had a problem flying my Supercub in Texas, before boxing it up for the move to the UK. But then it really does come down to performance, doesn't it? Power to weight, lads, power to weight!

The only problem with flying a 150 hp Supercub in the UK is remembering NOT to enjoy max climb out of Wellesborne, and finding myself nose to tail with somebody doing that peculiar overhead join you Limeys employ....what's wrong with joining downwind?

"When in Rome, do as the Romans do"

because


in the downwind......

Try flying out of Ryiadh Saudi Arabia in July.

48 degrees C with dust in a AC685 over gross.

Book figure was 4,000 feet. I reckon we did 6,000 feet ground run

Like others from OZ we are all taught the effect of temperature on performance. Australia doesn't have too many runways above 3000 feet altitude, but inland temperatures are usually between 30 and 40 degrees.

Reading the books ?
 

All this thread seems to prove to me is how few people have properly digested the contents of the flight manual.

It would be nice to have a Flight Manual to digest. I have a few notes with VNE and max rpm, but no performance figures.

How can you not have a flight manual?

Is it not a legal requirement to have it on board when you fly?

That depends... My own pride and beauty is a Hungarian-built microlight, it does come with a P&OH but there is no mention of minimum runway requirements, nor of Vx, Vy, and so on. It was registered here in BE without any issue on that subject, though, and before that in HU.

I have a flight manual. It's for the wrong engine and propeller, has different rpm limitations for glider towing, and banner towing, compared to normal flight, And it's a scruffy bundle of A4 copies. But the CAA, who are never wrong, approved it and put their stamp on it.
So obviously I must abide by it, mustn't I ?
Fortunately I have a comfortable power weight ratio.

:)

Good morning Piper Classique!

Well done for picking up the important point I was trying to make....and sent all the hounds barking down the wrong track (when in Rome, etc etc.) I think I need to start a new thread about the overhead join!

Power to weight ratio really matters, it is quite uncomfortable to watch an overloaded Cessna with two fat guys and too much baggage labouring into the air on a hot day! Excuse - it took off OK in January, didn't it?

How many people tell the truth when calculating weight and balance and when did they last step on the scales with all their clothing, wallet, mobile phone, etc etc etc?

Sure helps to have a nice big engine.

Speaking of flight manuals, I too was flying in my Piper Supercub with a friend, and my trusty flight manual in the luggage rear compartment; an assembly of A4 pages in an A4 brown envelope. To the satisfaction of the legal requirement, for quite a few years.

We decided to fly with the door and window open, nice hot day. There is nothing like flying with the doors open in a Supercub to give the true sensation of being aloft! Looking down in a well banked turn, you can look past the maingear right down to the ground, nothing in the way at all at all.

So couldn't resist throwing GOFER around a bit, nice steep turn one way, then the other, and suddenly the brown envelope gave way, the A4 flight manual rose up and my back seat passenger was snowed under by flying pages of important information; she managed to grab most of them, a couple went outside, two pages clung to the empennage, and five were lost forever over the countryside. Oops!

O dear. It was very very funny. I made an executive decision to stop messing around and returned to base....the manual, with the missing pages recopied, was securely wrapped and bound, and still rides around in the aeroplane as required by the Authorities. Where the dickens we are supposed to carry the flight manual for a glider, when the only baggage space available is required for a bottle of water (to drink) and a banana...far more use than a flight manual ... no way you could refer to it in flight anyway without compromising your lookout!

Mary
 

What do you sugest the authorities mandate when it comes to flight manuals ?

You are looking at the situation from the glider pilot point of view, gliders very rarely go anywhere apart from flying around on comps, your take off performance is dictated by the tug or winch ( except on those tubo things with lawn mower engines) so for what you do carrying the flight manual is not very useful.

Now put yourself in the position of a flying club member who has hired an aircraft to go touring, I would think you would want to take a look at the flight manual when about to fly your wife & kids out of an airfield near Madrid with an OAT of 35 C.................. You might even decide not to fly !

The only way to make sure that the pilot of an aircraft has the information to fly the aircraft safely is to mandate that the Flight manual stays with the aircraft, this may be impractical in some aircraft but I can't see another way of doing this. It is not because you air expected to consult the manual in flight.

Whilst we dont quite get those temps in Aus (well most places anyway) when in the peak of summer it encourages you to get that big fan running up front! Somehow, I always manage to get stuck behind 2 or 3 whilst waiting to enter the runway and there always seems to be 2-3 in the pattern getting ready to land!

Er, excuse me but gliders regularly go cross country. Just that usually they don't make intermediate landings. I got trailered out of a field today....
Grrr

I trust the field you chose for your outlanding was big, flat, clear of crop or animals, and convenient to a nice restaurant!

Flying gliders cross country does lead to interesting experiences. Meet the locals, treat the crew to a good meal after derigging the glider....and most of all, fun to talk about later with your friends...

What do power pilots have to talk about?

mary power pilots often reminisce about the exciting days when flying was dangerous, sex was safe and checklists hadn't been invented. oh and women, grog, women, booze, the weather and sometimes even women.
did I mention women ? yeah thats what we talk about, oh and aeroplanes.

Self-launching gliders have quite complex and not very powerful engines, often take off with ballast thus heavy and you better do your calculations with gliders too....

Hi Mary. The field was fine, the access road a bit less so. Mind,a standard Mucha doesn't need a very big field. It does need thermals at regular intervals. But, I was given coffee and cake at the nearest house, and played with their kitten while waiting for crew. And they helped us derig. So, all well there. I would be ashamed to admit how little distance I covered, so I won't, except to say that one third of a task is a bit feeble. Going to play with the balloon tonight, I hope.

Back on track, I come from the same neck of the woods as Piperboy. A few years ago I took my old Beagle Terrier to France. It drank petrol and oil but a nice way to watch the scenery go by.

Part of the holiday included a visit to Disney and the easiest airfield is Lognes. We were parked on the grass beneath the tower. After dropping off the hire car we sat under the wing drawing lines and things. I tried to get them to take a landing/parking fee but they refused. So all the stuff back in the plane and off we went...

The hard runway is 700m and I usually operated out of a 450m grass strip. We used 500m plus of the runway and almost relied upon the curvature of the earth to climb. The Terrier had a much stamped up handbook with charts for everything, including density altitude corrections for the distance to clear 50ft.

The book said it would be easy - circa 300 - 350 yards, the aircraft seemed to think otherwise. In subsequent visits to warmer climes we noticed what seemed to be a disproportionate drop off in performance once the temperature got over 25 deg C. But in 'normal' Scottish temperatures it met the book figures easily.

What it must have been like using them for spraying in the Sudan and similar places goodness knows but the Gypsy/Auster combination does not like heat (I've never had the opportunity to try just height!).

Always nice to have bright sunshine and cold air.... climbed out at 1,200'/min in an ancient C-150 last Winter... though the -35c helped.

And down in FL it is nice when they give you the Density Altitude in the ATIS.

"Did he just say 7,000'???? We're 100'ASL!" :}

With a single seat glider, you know you will be fine if the towplane got the glass 2-seater up;)

The other important temperature limitation is on trailer retrieves, especially considering crew age -- bring beer.

As part of the high temperature landout kit, it can help farmer relations:\

Yes, the landing ground roll increases.

Whilst I tend to agree with A and C's sentiment regarding flight manuals, I do wonder whether pilots understand the absolute basics.

L = Cl x 0.5 x RHO x Vsquared x S

If RHO is a smaller number V will need to be a bigger number :)

As a True Airspeed yes, as an Indicated Airspeed no

I do believe that was the point cows getting bigger was making......

More high than hot in this case, but a valid lesson in density altitude calculations nevertheless!

A factor which can affect hot and high performance of light aircraft is the pilot. The pilot either knows, or rapidly notices that the takeoff performance will be less, due to hot and/or high. This increases the "urgency" to get airborne from the available runway. The result can be prerotation, and high drag, which extends the run, and further degrades performance.

There comes a point where you determine before the takeoff roll, that you must make the most of what you have, as there is little excess. For these takeoffs, the determination of a reject point is important, and then purposefully allowing the aircraft to accelerate as much as possible, with the least drag, through each phase of the takeoff.

This is to be coupled with the other reality: Obstacles. Eventually, your takeoff path will encounter one. If it is close, all you have to do is safely clear it. You don't have to clear it by 250 feet, or even 100 feet, it things are critical. Just clear it. Refer to my thread on "Height Velocity Curve", which linked to obstacle clearance will suggest that you'd rather clear it safely with a reserve of speed and energy, than try to clear it by a much greater margin, for no good reason, and give up that safely buffer of speed and energy.

Yes, hot and high does affect performance, but so does pilot technique. Surprised and disappointed pilots like to blame the conditions, but sometimes technique played a role too....

Two points - when BA substituted 747s for the Tristar that had a "heavy" landing, the first one provided was P & W engined - it only just got off from MPA, and at Ascension, because BA insisted on day time flights only, its take off from ASI was very marginal, in fact the Fire Crew commander had the fleet on the run at three quarters of the way down the runway.


Secondly, here in France I have seen gliding for the day cancelled when it is very hot (31C here today, forecast 37C tomorrow) because the tug cannot get the tow off the ground in the take off distance available. Also it can be unbearably hot in the aircraft