Some clarity required on Decision Altitudes
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Some clarity required on Decision Altitudes
Chaps/Chapesses,
What is your take on DAs
I have been trained to wait until DA(+Pressure Error Correction) before looking up and following the routine of "DA, nothing seen, going around"
Example DA 560ft PE of 20ft, DA to look up @ 580ft...
So it goes like this "600ft, 590ft, 580ft, DA, looking up, nothing seen, going around"
In the time it takes to perform that, you may drop 40ft, so down to 540ft say before the AC levels and the go around comes about.
With the above situation would you normally fail your precision approach on an IRT, as that situation resulted in me failing my precision approach on my IRT, I'm a bit frustrated as that was how we were taught to do it!
Any views reccomendations for my resit appreciated.
Windy
What is your take on DAs
I have been trained to wait until DA(+Pressure Error Correction) before looking up and following the routine of "DA, nothing seen, going around"
Example DA 560ft PE of 20ft, DA to look up @ 580ft...
So it goes like this "600ft, 590ft, 580ft, DA, looking up, nothing seen, going around"
In the time it takes to perform that, you may drop 40ft, so down to 540ft say before the AC levels and the go around comes about.
With the above situation would you normally fail your precision approach on an IRT, as that situation resulted in me failing my precision approach on my IRT, I'm a bit frustrated as that was how we were taught to do it!
Any views reccomendations for my resit appreciated.
Windy
Isn't the DA exactly that....descision altitude (not a minimum descent altitude), so naturally the aircraft may descend slightly through that height as you make the 'D' to and then execute the missed approach?
I have done this on all of my IRTs and it certainly hasn't resulted in a fail...descending below an MDA on a NPA is a different kettle of fish though.
Turkey
I have done this on all of my IRTs and it certainly hasn't resulted in a fail...descending below an MDA on a NPA is a different kettle of fish though.
Turkey
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DA has a zero tolerance in one direction only. If you want to pass an IRT then make your decision before you get there and make sure that you do not descend below it. No IRE can fail you for that but they can all fail you for descending below it.
Haven't read the regs recently (perhaps I had better) but from a practical perspective what does a heavy jet do on a CAT 1 ILS....do they commence a missed approach 200 odd feet above the DA just in case they don't get visual at the DA?(I am not a heavy jet driver so I don't know).
Cheers
Turkey
Cheers
Turkey
Don't agree I'm afraid. MDA is a minimum which you must not go below on a non-precision approach.
DA is exactly that, a decision altitude where you make your decision, if you go below it commencing your go-around that should not be a fail.
DA is exactly that, a decision altitude where you make your decision, if you go below it commencing your go-around that should not be a fail.
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I believe that you must decide and initiate a go around by DA, but there it is accepted that downward momentum will carry the aircraft below DA before the effect of raising lever and/or nose has caused a positive rate of climb. In other words you have to initiate (ie moved the controls) at or before DA. But the best thing is to ask you instructor who will know the policy of the examiner.
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Decision Altitude is the altitude at which the decision is made and it is acceptable for the aicraft to descend below this altitude during the go-around manoeuvre. Each class of aircraft has a different DA based on weight which accounts for the "dip" below the DA; helicopters are Class A along with light fixed wing aircraft.
As an aside, during a LPC or OPC the decision may be made up to 50' above the actual DA, something which I have seen used to good avail by many pilots over the years!
As an aside, during a LPC or OPC the decision may be made up to 50' above the actual DA, something which I have seen used to good avail by many pilots over the years!
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CRAB (and others) has it right, spoke to a CAA TI recently on the subject
1. MDA - tolerance is +50' -0'
2. DA - go around must be initiated by, tolerance +50' (useful if you are getting a bit ragged at the bottom on a proficiency check!) and -0', in other words the DECISION to go around must be made NOT BELOW the DA. As this nearly always coincides with an (in)voluntary pull with the left hand its not a problem! If you get to DA, then look up, then say "nothing seen".......you will have passed below DA and the decision has not yet been made so....
He mentioned that big jets with a DH of 100' above the runway may actually touch the runway during the go-around!
As always practicalities rule and if you want to be sure of passing a check, use the +50' tolerance, you cannot be failed for that.
1. MDA - tolerance is +50' -0'
2. DA - go around must be initiated by, tolerance +50' (useful if you are getting a bit ragged at the bottom on a proficiency check!) and -0', in other words the DECISION to go around must be made NOT BELOW the DA. As this nearly always coincides with an (in)voluntary pull with the left hand its not a problem! If you get to DA, then look up, then say "nothing seen".......you will have passed below DA and the decision has not yet been made so....
He mentioned that big jets with a DH of 100' above the runway may actually touch the runway during the go-around!
As always practicalities rule and if you want to be sure of passing a check, use the +50' tolerance, you cannot be failed for that.
Best not to reinvent the wheel - go to the relevent guidance; in this case the FAA provide the more concise guidance.
From FAA Notice N 8000-340:
In a monitored approach (for a two crew operation) the landing pilot, who is the monitoring pilot - i.e. NHP for the instrument part of the approach - makes the decision. As the aircraft approaches the decision point, the HP will call 'decide'; in the absence of a response from the landing pilot, the HP will initiate a go-around. In airlines, the landing pilot (monitoring pilot) is usually the PIC - this makes for better decision making (for obvious reasons).
In a single pilot approach, the auto-pilot acts as the HP and the landing pilot makes the decision to land or go-around; that is why there is (usually) an add-on of 50ft to the DA(H).
All aircraft will 'mush through' the DA(H) with a last second decision to go-around; this is accounted for in the calculations of DA(H). The approach ban was introduced to avoid such situations.
Jim
From FAA Notice N 8000-340:
From an operational viewpoint, DA(H) is the limit to which a pilot can descend before having to decide to continue the approach by visual means. If the visual references required to safely continue the approach have not been established before passing DA(H), a missed approach must be executed at DA(H). This does not mean that a pilot waits until arriving at DA(H) before deciding to go-around or to continue the approach based on visual references. The decision making process begins when the approach is initiated and continues throughout the approach. A pilot must continually evaluate course and glidepath displacement information throughout the approach. Knowing that significant changes cannot occur instantaneously, a pilot begins to formulate a decision concerning the probable success of the approach long before reaching DA(H). Although DA(H) is a specified point in space at which a pilot must make an operational decision, the pilot accumulates the information required to make that decision throughout the approach. It is incorrect to assume that all aspects of the decision making process are delayed until the critical instant the aircraft arrives at DA(H). The visual cues, which become available during the descent to DA(H) enhances the pilot’s formulation of the decision, which must be made at DA(H). The operational decision to continue the approach by visual means, however, must be made before passing DA(H). At DA(H), a decision to continue the approach by reference to visual cues is appropriate if a pilot is satisfied that the total pattern of the visual cues provides sufficient guidance and the aircraft is in a position and tracking so as to remain within a position from which a safe landing can be made. However, if a pilot is not satisfied that all of these conditions exist, a missed approach must be executed.
The decision that the pilot must make before passing DA(H) is not a commitment to land. It is a decision to continue the approach based on visual cues. This distinction is important since the possibility exists that, after passing DA(H), visual cues may become inadequate to safely complete the landing, or the aircraft may deviate from the flightpath to a point where a safe landing cannot be assured. Since many variables are involved, the final decision to commit to a landing is the PIC’s and is primarily a judgment based on all the relevant operational factors. The PIC shall usually delay the decision to commit to a landing until the final stages of flare and landing.
(1) The following is a list of statements that describe what DA(H) is:
• DA(H) is a specified decision point.
• DA(H) is the point at which a specific action must be initiated (either continue the approach by reference to visual aids or go-around).
• DA(H) is the lowest permissible height to which an approach with vertical guidance can be continued by reference to flight instruments alone.
• DA(H) is the limit to which a pilot can descend before having to decide to continue the approach using external visual references.
(2) The following is a list of statements that describe what DA (H) is not:
• DA (H) is not a point where a decision or commitment to land is made.
• DA (H) is not a point where the decision-making process begins.
• DA (H) is not the latest point at which a go-around could or should be made.
• DA (H) is not a point where all aspects of the decision are instantaneously formulated.
The decision that the pilot must make before passing DA(H) is not a commitment to land. It is a decision to continue the approach based on visual cues. This distinction is important since the possibility exists that, after passing DA(H), visual cues may become inadequate to safely complete the landing, or the aircraft may deviate from the flightpath to a point where a safe landing cannot be assured. Since many variables are involved, the final decision to commit to a landing is the PIC’s and is primarily a judgment based on all the relevant operational factors. The PIC shall usually delay the decision to commit to a landing until the final stages of flare and landing.
(1) The following is a list of statements that describe what DA(H) is:
• DA(H) is a specified decision point.
• DA(H) is the point at which a specific action must be initiated (either continue the approach by reference to visual aids or go-around).
• DA(H) is the lowest permissible height to which an approach with vertical guidance can be continued by reference to flight instruments alone.
• DA(H) is the limit to which a pilot can descend before having to decide to continue the approach using external visual references.
(2) The following is a list of statements that describe what DA (H) is not:
• DA (H) is not a point where a decision or commitment to land is made.
• DA (H) is not a point where the decision-making process begins.
• DA (H) is not the latest point at which a go-around could or should be made.
• DA (H) is not a point where all aspects of the decision are instantaneously formulated.
In a single pilot approach, the auto-pilot acts as the HP and the landing pilot makes the decision to land or go-around; that is why there is (usually) an add-on of 50ft to the DA(H).
All aircraft will 'mush through' the DA(H) with a last second decision to go-around; this is accounted for in the calculations of DA(H). The approach ban was introduced to avoid such situations.
Jim
Last edited by JimL; 10th Oct 2009 at 16:11.
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In a monitored approach (for a two crew operation) the landing pilot, who is the monitoring pilot - i.e. NHP for the instrument part of the approach - makes the decision. As the aircraft approaches the decision point, the HP will call 'decide'; in the absence of a response from the landing pilot, the HP will initiate a go-around. In airlines, the landing pilot (monitoring pilot) is usually the PIC - this makes for better decision making (for obvious reasons).
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The theory is fine but Windy failed his IRT by descending below DA. I still think that not descending below the DA in a helicopter is the way to pass an IRT.
In a non-test situation in marginal conditions I would wait until DA but with an IRE watching my LPC I will be calling 'decide' about 30 feet above DA.
In a non-test situation in marginal conditions I would wait until DA but with an IRE watching my LPC I will be calling 'decide' about 30 feet above DA.
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I think it's one to put down as a lesson learnt, if you've got +50ft to use then use it, and keep clear of your minimums, then no one can complain! It's just an expensive lesson at £3000 per test, and damn frustrating!
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From my copy of FLIGHT EXAMINER (HELICOPTERS) HANDBOOK
Tolerances for starting go-around at decision alt/ht are: +50ft/-0ft,
(SE +100ft/-0ft)
Remember that this is a TEST! What you (and I) do in real life is not relevant here.
Add 50', get within tolerance and then go-around!
You might not agree, but at least you will pass.
Tolerances for starting go-around at decision alt/ht are: +50ft/-0ft,
(SE +100ft/-0ft)
Remember that this is a TEST! What you (and I) do in real life is not relevant here.
Add 50', get within tolerance and then go-around!
You might not agree, but at least you will pass.
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Crab and Tomo and 100% correct in that you make the decision at DA, +50' -0'.
If an IRE failed a pilot for going below the DA, when having made the decision by,or at DA, then the IRE is most certainly incorrect in failing the pilot.
If an IRE failed a pilot for going below the DA, when having made the decision by,or at DA, then the IRE is most certainly incorrect in failing the pilot.
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Windy,
Assuming it didnt take you 10 secs to say "DA, looking up, nothing seen, going around" and then pull the collective (which would have left any examiner unimpressed), I think we could say he/she was being a bit picky. Unfortunately CAA examiners are the most demanding I have come across. I have seen European and FAA examiners who are like Father Christmas in comparison. Having acted as copilot for people taking multi-crew check rides with FAA examiners, I have been absolutely certain that the result was a fail, (the test having taken 3 1/2 hours, because they kept screwing up the approaches!) yet seen the examiner shake their hand and congratulate them at the end!
Assuming it didnt take you 10 secs to say "DA, looking up, nothing seen, going around" and then pull the collective (which would have left any examiner unimpressed), I think we could say he/she was being a bit picky. Unfortunately CAA examiners are the most demanding I have come across. I have seen European and FAA examiners who are like Father Christmas in comparison. Having acted as copilot for people taking multi-crew check rides with FAA examiners, I have been absolutely certain that the result was a fail, (the test having taken 3 1/2 hours, because they kept screwing up the approaches!) yet seen the examiner shake their hand and congratulate them at the end!
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us airlines
Once a helicopter pilot, then an airline pilot and now a helicopter pilot. In a DC-9 on an ILS approach you continue at 700 fpm rate of descent(average based on usual approach speeds) until reaching DA, then make your decision. There is no way you will stop your descent at the DA, ever. You will pass through it coming down and going back up, if you miss. You do not level off prior to the DA or you will lose the glideslope. When you are only 200 feet above the ground, (100 for CAT II) the slightest attempt to level off will throw you off the slope full deflection very quickly. If that happens during any phase of the approach you should go missed. The rule is the same for any aircraft. Now, in a helicopter doing 70 KIAS instead of 140 KIAS you should make your decision and pass through the DA more quickly coming down and going up, but in either case you should never stop at the DA. If you do then you have not performed an ILS approach correctly. The MDA is totally different and the requirements should never be confused in any way with the DA. One is an altitude that is the absolute minimum until reaching the MAP the other is only a point in space where a decision must be made. Cheers
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Anyone else here nervous with the attitude of "if I were doing it for real, then I'd do it differently"? Surely one should practice their IMC flying skills to the minimums so that you have the ability to fly safely to those limits when you HAVE to. Remembering of course that most people practise IF in good weather under the hood, not in the turbulent uncomfortable conditions that generally go hand in hand with an IF approach to minimums...
Oh and for the record, I agree with Crab as well........
Oh and for the record, I agree with Crab as well........