Hot temp platform approach

[MD83FO]

Hello,

I like to calculate mi NPA profile to correct for hot OAT just like i do in cold weather, this changes the indicated altitude over the FAF to read below published, how legal is this?, I'm sure many instructors wont like it.
What i do to avoid this is to change the flight path angle by .2 degrees or so, though id like to stick to the 3 deg.

I'd appreciate inputs, thanks

[divinehover]

In hot condition you will be higher on the approach and therefore on the 'safe side'. There is no need to correct for been high. Just be aware that on steeper than normal approaches (3.2deg or greater), in hot conditions, for might find it difficult to stabilise your speed due high approach angle.

[Storm Girl]

Excellent answer. Simple and correct.

[compressor stall]

"What i do to avoid this is to change the flight path angle by .2 degrees or so, though id like to stick to the 3 deg."


Why?

[MD83FO]

If you don't correct for hot weather you'll be above glide path on the entire approach, thats why i do it.
im just doing the same thing an ILS glide slope does, if you have noticed in hot weather you will cross the FAF on the GS at a lower indicated altitude.

[MD83FO]

John Smith, does invention require you to come up with something new?

[MD83FO]

hello DOT I fly for Qatar Airways and I use an application called airports with an approach path calculator, you dial in the initial approach altitude, the runway elevation, descent angle and temperature. works great in the 50 degree weather of Doha, but I also used it in Kathmandu and Sanaa before use start RNP AR.
tell me this is lack of airmanship.

[1jz]

Well very nice that you are interested in new additions for the betterment but, you need to get the procedures approved before you actually use it. You can't just follow your brain waves.

Take my advise, delete your posts before Qataris find out your E=mc2 formula.

[FlightDetent]

The formula is right there, in Doc 8168. When the temps are extreme, I do those calculations as well. Being 400 ft above on a 6 mile NPA has its meaning. But only for awerness, no change to FCU settings. I do call this airmanship.

[Amadis of Gaul]

Just fly the goshdarn airplane, this isn't rocket science, really. 3.0deg and 3.2 is close enough for guvmint work.

[de facto]

As you dont change actual altitudes,you can always brief your increased TAS due to temperature and brief expected descent rate,your instructor will be happier.:E

[MD83FO]

I love rocket science, and sometimes I feel ashamed of saying I'm a pilot thanks to the level of mediocrety I see.

[compressor stall]

So you are cleared to 3000 in readiness for an ILS approach.

It's isa +30.

Are you seriously saying you'd level out at 2640'. ?

ATC might have something to say as well...

[Skyjob]

I love rocket science, and sometimes I feel ashamed of saying I'm a pilot thanks to the level of mediocrety I see.


The mediocrity in this thread is unfortunately displayed by yourself.
Agreed as per previous commentators, you DO NOT change procedures which are created to keep you safe from terrain.
Being a bit too high on such approaches due to (very) high temperatures is safer than being too low making an incorrect correction for it.
There is indeed documentation on the HOW to do such thing, they are meant for procedure designers, not pilots personal use to correct established, approved and authorised approach procedures.

However, I can see you strongly feel about this.
So why won't you submit this change of procedure in a formal proposal to relevant authorities?
Maybe, just maybe, if reasoned properly, changes to established procedures when confronted with extremely hot conditions as described, could be made available to all other aviators. But these changes need to be thoroughly examined, documented and ratified prior to use, which is where the authorities would need to come in.
Rather than fly these procedures now already, put your efforts into a formal proposal for improvement to the authorities.

Until then, please don't change the altitudes and angles of procedures which were designed to keep (all of) us safely away from ground. Remember, CFIT was not too long ago the main reason for deaths in aviation.

[despegue]

As long as you are under radar control, under NO CIRCUMSTANCES shall you correct on your own for temperature!:rolleyes:

[1jz]

Let's take it this way. God forbid you face an incident, even if it's not your fault, you will definitely be questioned about your HUMIDITY COMPENSATION LAW. Prepare yourself for that then.
Btw is it a single pilot operation? What's the other guy doing when you are experimenting?

[I-2021]

Some of the above comments have the only objective of creating a conflict and raising the stress level of this simple discussion. People are entitled to ask questions and you are entitled to your answers. The aim of a professional forum is to provide constructive answers and to avoid generating a never ending argument out of nothing. The user asked about the legality of his thoughts and asked for inputs as well, doesn't look like a big deal does it ?

[777AV8R]

The CAA better not know that you are using unapproved methods of calculating approach information, especially that of RNP-AR. The data being presented was developed through Airbus and flown by the airline, airbus and the CAA. Warning Flags!

[B737900er]

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

[TwoTone-7]

B737900ER

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

[MD83FO]

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.


www.developpement-durable.gouv.fr/IMG/pdf/ST-GuideO1-_PBN-RNAV_GNSS__ENGv3.pdf

[Georgeg13]

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

[Amadis of Gaul]

I love rocket science, and sometimes I feel ashamed of saying I'm a pilot thanks to the level of mediocrety I see.



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

[Skyjob]

MD83FO: Please be aware of the following abstract:
On certain avionics equipment, it is possible to enter the temperature at the airport, so that the system can correct the vertical profile in Baro VNAV.

But if the equipment is unable to correct for it, you do not do it yourself.

[FlightDetent]

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

[heavy_landing]

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.

[TwoTone-7]

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! :))

[TwoTone-7]

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?!

[FullWings]

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...?

[jack schidt]

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