The cause of unstable approaches
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The cause of unstable approaches
I can't see how unstable approaches can happen among professional pilots. If you're not stable at 1000', go around. It should be obvious if this is going to happen at 2000' and even at 3000' (9.4 miles away) it shouldn't be too hard to work out.
So why does it happen? Is it poor skill, poor judgement, poor self control or something else?
So why does it happen? Is it poor skill, poor judgement, poor self control or something else?
I can't see how unstable approaches can happen among professional pilots.
One example - By your logic going down the slope into LHR looks simple and "unbustable", after all what can go wrong given a 9 or 10 mile final? Well LHR's seemingly benign standard requirement of "160 to 4", if adhered to both down to the knot and the tenth of a mile (which we all do of course)
can make being stable at the 1000 foot gate a bit sporty on some types in some conditions with some weight/flap combinations.
It should be obvious if this is going to happen at 2000' and even at 3000' (9.4 miles away) it shouldn't be too hard to work out.
Umm...ROFL...In an ideal world with no speed control maybe (see above) ...... In the real world, or parts thereof the problem is often along the lines of:
"Go direct to the FAF, keep the speed up, you're cleared for the ILS, maintain 180 to 5" ......
Sure you'll try, but frankly somedays, being professional or not, circumstances conspire to ensure you haven't get a cat in h*lls chance of making the 1000 gate....
Last edited by wiggy; 26th Feb 2014 at 18:43. Reason: reformat/spelling/typos
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If your profile is reflective of your current experience then keep your head down in the RHS and learn from the old wise ones on your left shoulder. Being gods gift to aviation tends to have a short life expectancy.
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dear OP:
if you are stable at 900' even though you should have been stable at 1000', would you go around?
how much fuel is used in a go around on your plane? how much is that in dollars?
yes, things SHOULD be one super way
but they aren't
they are real.
and I am an advocate of stable approaches in every type of plane
if you are stable at 900' even though you should have been stable at 1000', would you go around?
how much fuel is used in a go around on your plane? how much is that in dollars?
yes, things SHOULD be one super way
but they aren't
they are real.
and I am an advocate of stable approaches in every type of plane
Sometimes it can be caused by aiming to be stable at the last possible time. E.g., if your requirement is to be stable at 1000' and you aim to just get stable at that time then you have a high risk of getting it wrong. Airport requirements for 160 knots to 4NM and the like doesn't help. If followed to the letter that'll give you about 200-300' to get stable. If you're in a heavy jet it might not be a big adjustment, in a light jet with Vapp of 120 knots it can be harder. A good crew would prioritise being stable over the speed restriction and reduce speed earlier if required. The point remains that it is forcing you to aim to be stable at the last possible point rather than comfortably getting stable well before hand.
Our requirement is to be stable by 500' in VMC and 1000' in IMC. My plan then is to take the last stage of flap approaching 1000' and 1500' respectively, this gets me stable comfortably before I'm required to be. What you're doing at 2000' and 3000' has little bearing on anything. You could be chugging along at 200 knots at 2000' and 250 knots at 3000' with a good plan to get stable later on. You don't know yet that your plan is about to go wrong (for whatever reason.)
Our requirement is to be stable by 500' in VMC and 1000' in IMC. My plan then is to take the last stage of flap approaching 1000' and 1500' respectively, this gets me stable comfortably before I'm required to be. What you're doing at 2000' and 3000' has little bearing on anything. You could be chugging along at 200 knots at 2000' and 250 knots at 3000' with a good plan to get stable later on. You don't know yet that your plan is about to go wrong (for whatever reason.)
What you're doing at 2000' and 3000' has little bearing on anything. You could be chugging along at 200 knots at 2000' and 250 knots at 3000' with a good plan to get stable later on. You don't know yet that your plan is about to go wrong (for whatever reason.)
Yes, the old slow down early, descend early but get ready to be rushed routine beloved of many destinations world wide..(though obviously not destinations frequented by the OP).
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As AerocatS2A has mentioned improper planning and poor situational awareness are key components of unstabilised approaches. Aiming to be stablised at 1000' give little room for errors in what is very dynamic environment filled with vast amounts of variables.
But this does answer the why question?
sure we can quantify the approach phase and sum up on how the approach unfolded but more often then not the underlying cause is still left unanswered, why crews neglect the stabilised approach criteria and still continue the approach <1000'.
look at it from a cognitive point of view, as human were a tendency to be loss averse (loss aversion) which refers to people's tendency to strongly prefer avoiding losses to acquiring gains which in tern may prompt us to take on more risk. Loss aversion vs Risk Aversion theories and decision making are well documented within the investment and economics domain.
put simply regardless of the sequence of event leading up to the 1000' gate.. what prevents the crews from going around....uncertainty...
But this does answer the why question?
sure we can quantify the approach phase and sum up on how the approach unfolded but more often then not the underlying cause is still left unanswered, why crews neglect the stabilised approach criteria and still continue the approach <1000'.
look at it from a cognitive point of view, as human were a tendency to be loss averse (loss aversion) which refers to people's tendency to strongly prefer avoiding losses to acquiring gains which in tern may prompt us to take on more risk. Loss aversion vs Risk Aversion theories and decision making are well documented within the investment and economics domain.
put simply regardless of the sequence of event leading up to the 1000' gate.. what prevents the crews from going around....uncertainty...
- go arounds are not conducted on a frequent basis hence reluctance initiate once can be borne.
- Operational consideration (duty, time, connecting transit pax, next sector departure time..etc)
- WX
- Fuel
- and others
- ATC, traffic
- other i can think of right now
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Surely it depends which of the stabilised criteria you haven't met?
In our company (as I'm sure it's most) the main points are wings level, landing configuration, clear position to land without exceeding 1000 fpm RoD, and landing checks complete.
So if we're passing 500' (our lowest height to be stabilised) and don't yet have landing flap, it's clearly a go around, no questions asked.
But if it's 1000' on a precision approach (manual says MUST be stabilised here) and we're just on the last few points of the landing checks, but everything is set, are we going to go around? Probably not, yet by the definition we weren't stabilised.
So perhaps the stats show a lot of unstable approaches where pilots simply used their discretion. Of course I'm sure there will be plenty of cases of very late flap selection, beyond the point where the approach should have been stable, and perhaps that was poor judgement in when to start slowing down or configuring.
The most common I've seen is the need to keep a very high rate of descent during the last 1000', beyond what would qualify as stable (ie 4 whites or 3 whites and a "pink", but you think you can salvage it) and perhaps that is just poor judgement combined with poor self control, and a worry about having to explain the go around or look like you were a bad pilot for not being able to fly a simple approach, and then causing delays for passengers and possibly the rest of the day if you're already late. Of course, the better pilot would go around putting safety and stabilised criteria first, but in the heat of the moment it can be easy to try and salvage a poor approach.
In our company (as I'm sure it's most) the main points are wings level, landing configuration, clear position to land without exceeding 1000 fpm RoD, and landing checks complete.
So if we're passing 500' (our lowest height to be stabilised) and don't yet have landing flap, it's clearly a go around, no questions asked.
But if it's 1000' on a precision approach (manual says MUST be stabilised here) and we're just on the last few points of the landing checks, but everything is set, are we going to go around? Probably not, yet by the definition we weren't stabilised.
So perhaps the stats show a lot of unstable approaches where pilots simply used their discretion. Of course I'm sure there will be plenty of cases of very late flap selection, beyond the point where the approach should have been stable, and perhaps that was poor judgement in when to start slowing down or configuring.
The most common I've seen is the need to keep a very high rate of descent during the last 1000', beyond what would qualify as stable (ie 4 whites or 3 whites and a "pink", but you think you can salvage it) and perhaps that is just poor judgement combined with poor self control, and a worry about having to explain the go around or look like you were a bad pilot for not being able to fly a simple approach, and then causing delays for passengers and possibly the rest of the day if you're already late. Of course, the better pilot would go around putting safety and stabilised criteria first, but in the heat of the moment it can be easy to try and salvage a poor approach.
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There are airports where the stable apch requirements simply cannot be met.
The FAA allows such things.
So, if I can be unstable at 400' but land safely at some airports, why not others?
(playing devils advocate here, as I really do believe in stable apch)
The FAA allows such things.
So, if I can be unstable at 400' but land safely at some airports, why not others?
(playing devils advocate here, as I really do believe in stable apch)
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The post has been started either by a troll and/or someone who is truly ignorant of real world aviation. However, I shall slightly rise to the bait. Firstly, the stablisation criteria have been slightly overlooked. Also, are we talking about VMC or IMC? What sort of aircraft? Short haul or long haul? Where is the airport? What are the conditions? And how much fuel do we have? Now, not for one minute am I suggesting that we should not fly stablised approaches, but adherence to simple rules to control complex dynamic scenarios generally only leads to misery. So what is the solution? That is as complex as the problem but it starts with an understanding of the problem, training, support from the company and above all, a flight crew who strive to operate in a professional manner.
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Been reading this thread with much interest. Altough I am not a pilot I have always had a strong interest in aviation and am a much travelled passenger. So then, as I have only recently came across this "stable / unstable approach business perhaps someone can explain just what constitutes stable and unstable approaches and are there official requirements. Do these requirements change by company. I say this as I have noted over the years that when Ryanair used to operate into Teesside they where always established on final approach well before the outer marker whereas KLM frequently pass right over my house on left base to turn onto finals at about a mile and a half at most.
Thanks
Thanks
Do these requirements change by company
For us:
At 1000 "agl" ( irrespective of being IMC or VMC) we must be fully configured, landing checklist complete, and on the vertical profile. Final Speed and approach power must be achieved by 500 agl. Wings must be level by 300'.
...whereas KLM frequently pass right over my house on left base to turn onto finals at about a mile and a half at most.
Last edited by wiggy; 28th Feb 2014 at 14:13.
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Reading the previous posts I am reminded of that old saying, “Pilots use their superior judgment to avoid having to demonstrate their superior skills.”
Just remember guys when passing 100 feet just ask yourself, “Am I safe to land,” if not Go Around.
Another circuit may require an explanation on the voyage report, but to run off the runway or worse will really spoil your day…
Just remember guys when passing 100 feet just ask yourself, “Am I safe to land,” if not Go Around.
Another circuit may require an explanation on the voyage report, but to run off the runway or worse will really spoil your day…
Do these requirements change by company
Large airline in Asia.
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Stabilisation criteria
From a medium sized European Airline:
...at the approach speed plus applicable additives, on the proper flight path, in the landing configuration, at the proper sink rate and with the thrust stabilized no lower than 1000 ft AFE when operating in IMC and 500 ft AFE for VMC operations.
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https://www.youtube.com/watch?v=5lAsALc6-mA
the low altitude turn is about 3 minutes, completing the turn gives you about 10 seconds wings level on final. you do the math
the low altitude turn is about 3 minutes, completing the turn gives you about 10 seconds wings level on final. you do the math
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It's called ENERGY MANAGEMENT and starts before the top of descent, continues ALL THE WAY DOWN TO THE LANDING THRESHOLD, preferably monitoring what HAL the FMS is saying and using simple but comprehensive mental maths to adjust the path.
Simples?!? But badly taught by those who should know better and are paid for that task.
Simples?!? But badly taught by those who should know better and are paid for that task.
