Asian pilots seem to have a habit of flying low approaches :}

B737900ER

That one is uncalled for, let's get back to the topic mate.

I'm not changing published altitudes as in cold weather, I'm merely calculating a temperature corrected path to cross the threshold at 50', and not reach the published MDH too high. and it is exactly what an RNAV BARO VNAV system will do for you on a NPA, if you care to have a look at the temperature correction of the PBN manual.


http://www.developpement-durable.gou...NSS__ENGv3.pdf

Except the conflicts,some really interesting things can be learned through this topic...:ok:

As do I, especially when I realize how many "pilots" can't even spell "mediocrity", despite ostensibly swimming in a veritable sea thereof.

MD83FO: Please be aware of the following abstract:
But if the equipment is unable to correct for it, you do not do it yourself.

What are all the insults good for? (skybob: you were the last to post, not the one targeted by this remark)

MD83FO,
I think it's admirable that you're trying to use technology and the enthusiasm of youth to make things easier for you.
BUT, unless it's an SOP for your airline, please don't do it.
Why are you willing to operate outside SOPs, using a procedure which is difficult for other crew to monitor, when there is a perfectly good SOP to operate to? Why put your neck on the line?
If you make an error using your procedure, do you think you'll get any thanks?
Fly the approach properly, accept that the slope is slightly steeper than normal......and go home safely.

Just descend at the normal descend point then fine tune your descent angle FPA to correct for the weather conditions. I've seen people do what the author does and really don't understand one bit of it during briefing.
Another thing is try telling a controller who has you radar identified, they won't be best impressed.
Keep it simple and fly safe! :))

Wait!! MD83FO!

Just read what you wrote about calculating a descent path to cross the threshold at 50 feet?!!!! Ehhh, do you not disengage the auto pilot at minimums or before that if visual, disengage flight director and engage TRK FPA and ask for RWY TRK to be set and fly visually.

On the JEPP charts you have the distance vs height layout to tell you exactly wether you are above of below the profile. Why try and make it astronaut business when it's not?!

I don’t know where this fixation for trying to make every approach into a 3deg one has come from. Yes, it’s a standard approach angle if there are no other considerations but there are plenty of approaches to large airports which are steeper for good reason. Guess what, you just brief and fly them!

The same for ISA+ effects. If the procedure is 3deg at ISA, then even ISA+30 will only make it just over 3.3deg - three whites and a red on a 3deg PAPI. Again, brief what you expect to see, why it’s like that and what you’re going to do about it in terms of approach stability and when you transition to the visual segment.

Until we switch to geometric altitude as a reference, we’re stuck with QNH/QFE/QNE and temperature effects. Unlike cold weather corrections, which being additive make you safer even if you get them wrong, rolling your own subtractive adjustments has much greater potential for dangerous error. And for what gain? So you can fly exactly 3degs? Why...?

ISA being 15 Celsius at Sea Level, lets assume the platform altitude is 2000ft AMSL where the runway elevation is practically at sea level.

For every 10C increase above ISA your height is increased by 4% and so at 40C as in Dubai you would use the following example.

40C - 15C or actual temp - ISA = +25C to ISA

+25C is made up of 10+10+5 or 4% + 4% +2% or 10% increase to your real actual altitude AMSL or Airfield altitude in this case.

So if, at 40C, you were servo altitude 2000ft then your real altitude would be 2200ft or +10% of the 2000ft servo altitude.

The NPA path angle in Dubai eg RNAV is deliberately 2.8 degrees so that in the majority of the hot weather, you are really 2200ft AMSL with your servo altitude at 2000ft. Now here is the trick, this now puts you 10% above the 2.8 degree approach path angle or thats 2.8 degrees +10% = 3.08 degrees or almost a normal stable approach path angle.

An ILS will always keep you on a 3degree angle if appropriate. Should a hot climate NPA set 3 degree app path angles, then on a 40 C day, you would be looking at a 3.3 degree approach, possibly becoming unstable and not understanding what's happening.

Long answer sorry, hope that helped.


Edit:- the continual 10% increase to your servo altitude, ie you are always 10% above that indicated on the servo altimeter (at 40 C), washes out down the approach, ie at 1000ft + 10% = 100ft higher and at 500ft only 50ft higher.

Rgds

Jack