Decision Height

[Bonchie]

I read on here the other day that some are using DH+80 to go missed so "you don't blow through the DH"...someone mentioned it in their checkride write-up as well.

I checked the PTS and while it does say you can not bust MDA (+100, -0 tolerance), for DH there are no such restrictions.

In the PTS it only says:

13. A missed approach or transition to a landing shall be
initiated at Decision Height.

14. Initiates immediately the missed approach when at the
DA/DH, and the required visual references for the runway
are not unmistakably visible and identifiable.

Where does it say that you can not descend below the DH when going missed at the DH? Naturally, you will because there is lag from the decision to throttles up/nose up.

My CFII (former USAF) says the DH is exactly what it says and that's how they used it when he flew C-17s. You make the decision there, not 80 feet above to ensure you don't descend below it.

Thoughts? (Checkride tomorrow).

 

[RussR]

You and your CFII are exactly correct - there is no requirement to not go below DA (it's called DA, not DH anymore, unless you're talking about Cat II, which I assume you aren't). DA is where the decision is made, and you are EXPECTED to sink below it - it's even accounted for in the TERPS design standards for obstacle clearance.

Whoever is going missed at DA+80 isn't doing it right. And in fact, that should be a bust in itself according to the PTS..

 

[Bonchie]

What I thought. Just wanted to double check I wasn't missed something.

 

[MAKG1]

You and your CFII are exactly correct - there is no requirement to not go below DA (it's called DA, not DH anymore, unless you're talking about Cat II, which I assume you aren't). DA is where the decision is made, and you are EXPECTED to sink below it - it's even accounted for in the TERPS design standards for obstacle clearance.

Whoever is going missed at DA+80 isn't doing it right. And in fact, that should be a bust in itself according to the PTS..

Huh?

14 CFR 91.175(c ) prohibits operating an aircraft below DA unless visibility meets minimums and the "runway environment" is in sight.

 

[Bonchie]

Huh?

14 CFR 91.175(c ) prohibits operating an aircraft below DA unless visibility meets minimums and the "runway environment" is in sight.

Decision Altitudes are designed for you to lag below them when going missed.

 

[MAKG1]

Decision Altitudes are designed for you to lag below them when going missed.

Sure, but the reg doesn't have an exception for a "missed approach in progress."

 

[Bonchie]

Sure, but the reg doesn't have an exception for a "missed approach in progress."

The PTS clearly states the decision happens at the Decision Altitude, with no tolerance for before it. No adding feet or making the decision early.

I think the way you square this is that once you go missed, you aren't purposely maintaining a descent below it, you are doing a missed approach at that point by which it's assumed (and designed for) that there will be lag below the DA.

 

[RotorAndWing]

Sure, but the reg doesn't have an exception for a "missed approach in progress."

Once again, someone is trying to read into the regulations something that isn't there.

The PTS clearly states the decision happens at the Decision Altitude, with no tolerance for before it. No adding feet or making the decision early.

I think the way you square this is that once you go missed, you aren't purposely maintaining a descent below it, you are doing a missed approach at that point by which it's assumed (and designed for) that there will be lag below the DA.

Exactly.

 

[write-stuff]

The PTS clearly states the decision happens at the Decision Altitude, with no tolerance for before it. No adding feet or making the decision early.

I think the way you square this is that once you go missed, you aren't purposely maintaining a descent below it, you are doing a missed approach at that point by which it's assumed (and designed for) that there will be lag below the DA.

Yep, that.

 

[Greg Bockelman]

Sure, but the reg doesn't have an exception for a "missed approach in progress."

Chapter and verse, please.

 

[unsafervguy]

91.175

(e) Missed approach procedures. Each pilot operating an aircraft, except a military aircraft of the United States, shall immediately execute an appropriate missed approach procedure when either of the following conditions exist:
(1) Whenever operating an aircraft pursuant to paragraph (c) or (l) of this section and the requirements of that paragraph are not met at either of the following times:
(i) When the aircraft is being operated below MDA; or
(ii) Upon arrival at the missed approach point, including a DA/DH where a DA/DH is specified and its use is required, and at any time after that until touchdown.

note it says at arrival, not before arrival.
bob


see rotor and wing we do agree every now and then....

 

[bobmrg]

The PTS clearly states the decision happens at the Decision Altitude, with no tolerance for before it. No adding feet or making the decision early.

I think the way you square this is that once you go missed, you aren't purposely maintaining a descent below it, you are doing a missed approach at that point by which it's assumed (and designed for) that there will be lag below the DA.

You're right. The operative word is "maintaining." Inertia will inevitably cause descent below the limiting altitude during the missed approach procedure.

Bob Gardner

 

[flyingron]

The word the regulation uses is "continue".

It says no person may continue an approach below the DH unless [runway environment in sight]. This is different verbage than the MDA which says you can't descend below the MDA.

 

[taters]

You and your CFII are exactly correct - there is no requirement to not go below DA (it's called DA, not DH anymore, unless you're talking about Cat II, which I assume you aren't). DA is where the decision is made, and you are EXPECTED to sink below it - it's even accounted for in the TERPS design standards for obstacle clearance.

Whoever is going missed at DA+80 isn't doing it right. And in fact, that should be a bust in itself according to the PTS..

 

[Gucci Pilot]

The word the regulation uses is "continue".

It says no person may continue an approach below the DH unless [runway environment in sight]. This is different verbage than the MDA which says you can't descend below the MDA.

 

[Kritchlow]

The word the regulation uses is "continue".

It says no person may continue an approach below the DH unless [runway environment in sight]. This is different verbage than the MDA which says you can't descend below the MDA.

I think you're reading too much into that. Generally "continue" on the ILS is more associatiated with a constant path descent (GS), whereas the MDA may be a dive & drive.

 

[DJTorrente]

Let's talk real politik here. If an IA candidate pilot starts the missed at DA+50', he's well within the PTS (-0/+100), and the DPE can't disapprove him for it. If the pilot makes his decision at DA+0, then executes the missed as the a/c continues to sink below DA, you've now got a matter interpretation as to whether the missed was timely executed.

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

 

[MauleSkinner]

Let's talk real politik here. If an IA candidate pilot starts the missed at DA+50', he's well within the PTS (-0/+100), and the DPE can't disapprove him for it. If the pilot makes his decision at DA+0, then executes the missed as the a/c continues to sink below DA, you've now got a matter interpretation as to whether the missed was timely executed.

I'll let somebody else look it up in the Instrument Airplane PTS! but that wouldn't fly for an ATP applicant...

12. Maintains a stabilized final approach, from the precision final approach fix to DA/DH, allowing no more than one- quarter scale deflection of either the glideslope or localizer indications, and maintains the desired airspeed within ±5 knots.​

You'd definitely exceed 1/4 scale deflection if you initiated the missed early.

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

Apparently the pilots you know are of a different mindset than the ones I know...and you know more of 'em.

 

[Kritchlow]

Let's talk real politik here. If an IA candidate pilot starts the missed at DA+50', he's well within the PTS (-0/+100), and the DPE can't disapprove him for it. If the pilot makes his decision at DA+0, then executes the missed as the a/c continues to sink below DA, you've now got a matter interpretation as to whether the missed was timely executed.

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

The trees will never grow into it. If they did, then we would be hitting them all the time while following the glide slope.

Published DA is decision altitude. Decision altitude is NOT DA + 50'

 

[RotorAndWing]

Let's talk real politik here. If an IA candidate pilot starts the missed at DA+50', he's well within the PTS (-0/+100), and the DPE can't disapprove him for it. If the pilot makes his decision at DA+0, then executes the missed as the a/c continues to sink below DA, you've now got a matter interpretation as to whether the missed was timely executed.

I take it you are not instrument rated.

There is no "interpretation", it's really quite clear. See the several explanations above in this thread.

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

I'm not really sure by what you mean. The approach criteria for an ILS would prevent a "50' FAA standard tree" to be in the approach plane area. If you are on GS at DA on a CAT 1 ILS, you certainly have a safe area to round through as you transition from approach to go around.

 

[genna]

Let's talk real politik here. If an IA candidate pilot starts the missed at DA+50', he's well within the PTS (-0/+100), and the DPE can't disapprove him for it. If the pilot makes his decision at DA+0, then executes the missed as the a/c continues to sink below DA, you've now got a matter interpretation as to whether the missed was timely executed.

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

Nothing about -0/+100 past beginning of Final Approach Segment on Precision Approaches in PTS

There is no interpretation here. Decision Height/Altitude is where you make a decision. Anything else is not according to PTS. I was told that by my DPE as well


Task B: Precision Approach (PA)
[FONT=Arial,Arial][FONT=Arial,Arial]References: 14 CFR parts 61, 91; FAA-H-8083-15; IAP; AIM.
[/FONT][/FONT]Note: [FONT=Arial,Arial][FONT=Arial,Arial]A precision approach, utilizing aircraft NAVAID equipment for centerline and vertical guidance, must be accomplished in simulated or actual instrument conditions to DA/DH.
[/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]Objective: [/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]To determine that the applicant:
1. Exhibits adequate knowledge of the precision instrument approach procedures.
[/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]VI. Instrument Approach Procedures [/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]37 [/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]FAA-S-8081-4E
[/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]2. Accomplishes the appropriate precision instrument approaches as selected by the examiner.
3. Establishes two-way communications with ATC using the proper communications phraseology and techniques, as required for the phase of flight or approach segment.
4. Complies, in a timely manner, with all clearances, instructions, and procedures.
5. Advises ATC anytime that the applicant is unable to comply with a clearance.
6. Establishes the appropriate airplane configuration and airspeed/V-speed considering turbulence, wind shear, microburst conditions, or other meteorological and operating conditions.
7. Completes the aircraft checklist items appropriate to the phase of flight or approach segment, including engine out approach and landing checklists, if appropriate.
8. Prior to beginning the final approach segment, maintains the desired altitude ±100 feet, the desired airspeed within ±10 knots, the desired heading within ±10°; and accurately tracks radials, courses, and bearings.
9. Selects, tunes, identifies, and monitors the operational status of ground and airplane navigation equipment used for the approach.
10. Applies the necessary adjustments to the published DA/DH and visibility criteria for the airplane approach category as required, such as— a. NOTAMs
b. inoperative airplane and ground navigation equipment.
c. inoperative visual aids associated with the landing environment.
d. NWS reporting factors and criteria.
11. Establishes a predetermined rate of descent at the point where the electronic glideslope begins, which approximates that required for the aircraft to follow the glideslope.
12. Maintains a stabilized final approach, from the Final Approach Fix to DA/DH allowing no more than ¾-scale deflection of either the glideslope or localizer indications and maintains the desired airspeed within ±10 knots.
13. A missed approach or transition to a landing shall be initiated at Decision Height.
14. Initiates immediately the missed approach when at the DA/DH, and the required visual references for the runway are not unmistakably visible and identifiable.
15. Transitions to a normal landing approach (missed approach for seaplanes) only when the aircraft is in a position from which a descent to a landing on the runway can be made at a normal rate of descent using normal maneuvering.
[/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]VI. Instrument Approach Procedures FAA-S-8081-4E [/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]38
[/FONT][/FONT][FONT=Arial,Arial][FONT=Arial,Arial]16. Maintains localizer and glideslope within ¾-scale deflection of the indicators during the visual descent from DA/DH to a point over the runway where glideslope must be abandoned to accomplish a normal landing.
17. Uses MFD and other graphical navigation displays, if installed, to monitor position, track wind drift and other parameters to maintain desired flightpath.
18. Demonstrates an appropriate level of single-pilot resource management skills.
[/FONT][/FONT]
[FONT=Arial,Arial][FONT=Arial,Arial]Edit: bold by me
[/FONT][/FONT]

 

[genna]

Huh?

14 CFR 91.175(c ) prohibits operating an aircraft below DA unless visibility meets minimums and the "runway environment" is in sight.

[(c) Operation below DH or MDA. Except as provided in paragraph (l) of this section, where a DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, at any airport below the authorized MDA or continue an approach below the authorized DH unless-- ]

Operation is prohibited below MDA, not DA. Continuing approach is prohibited below DA. Different things. At DA you make decision to go missed and execute that, you are not continuing approach even though you descend below DA. It is not prohibited to descend below DA, only MDA

 

[Gucci Pilot]

Let's talk real politik here. If an IA candidate pilot starts the missed at DA+50', he's well within the PTS (-0/+100), and the DPE can't disapprove him for it. If the pilot makes his decision at DA+0, then executes the missed as the a/c continues to sink below DA, you've now got a matter interpretation as to whether the missed was timely executed.

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

It's called a decision altitude for a reason. The non-precision has a hard -0/+100 because it is a minimum descent altitude.

 

[hindsight2020]

Threads like this is why 'pilot' can't get you laid anymore. Jesus nerd Christ.

 

[aterpster]

Even if approaches are designed with margin for inertia to carry below DA while the missed in initiated, most pilots would rather have that margin than use it. Particularly for when the 50' FAA standard trees grow into it.

Indeed they are. You are not conversant with TERPs criteria. Not that pilots need be.

Do you have a cite for the 50-foot FAA standard tree? I'd like to learn about it.

 

[AlanM]

The ATP PTS states in Item V, Task F (Missed Approaches): "However, even if the missed approach is properly initiated at the DA/DH, most airplanes descent below DA/DH because of the momentum of the airplane transitioning from a stabilized approach to a missed approach. This descent below DA/DH is not considered unsatisfactory, as long as the precision approach was not continued below DA/DH.

And as previous stated by others, FAR 91.175(c) states: "No pilot may operate an aircraft....below the authorized MDA or continue an approach below the authorized DA/DH unless".....the three criteria are met, none of which refers to an MDA, DA or DH.

So much fuss over something clear as day. Forget the TERPS as there is no regulation and nothing in the AIM that says you have to know what criteria are used. Just know that the published approach procedure requires you to START the MA at the DA/DH.

And for those of you who say that, if one wanted to start a MA at some chosen amount of feet above the DA/DH because you don't understand the PTS and/or the regs, FAR 91.175(b) [the one just before (c)] states: "The authorized DA/DH or MDA is the highest of the following -- (1) the DA/DH or MDA prescribed by the approach procedure; (2) the DA/DH or MDA prescribed by the pilot in command; (3) the DA/DH or MDA appropriate for the aircraft equipment available and used during the approach."

All seems pretty clear with no interpretation needed, warranted or required.

 

[MauleSkinner]

The ATP PTS states in Item V, Task F (Missed Approaches): "However, even if the missed approach is properly initiated at the DA/DH, most airplanes descent below DA/DH because of the momentum of the airplane transitioning from a stabilized approach to a missed approach. This descent below DA/DH is not considered unsatisfactory, as long as the precision approach was not continued below DA/DH.

And as previous stated by others, FAR 91.175(c) states: "No pilot may operate an aircraft....below the authorized MDA or continue an approach below the authorized DA/DH unless".....the three criteria are met, none of which refers to an MDA, DA or DH.

So much fuss over something clear as day. Forget the TERPS as there is no regulation and nothing in the AIM that says you have to know what criteria are used. Just know that the published approach procedure requires you to START the MA at the DA/DH.

And for those of you who say that, if one wanted to start a MA at some chosen amount of feet above the DA/DH because you don't understand the PTS and/or the regs, FAR 91.175(b) [the one just before (c)] states: "The authorized DA/DH or MDA is the highest of the following -- (1) the DA/DH or MDA prescribed by the approach procedure; (2) the DA/DH or MDA prescribed by the pilot in command; (3) the DA/DH or MDA appropriate for the aircraft equipment available and used during the approach."

All seems pretty clear with no interpretation needed, warranted or required.

Note that the reg actually says "prescribed FOR the pilot in command", not "prescribed BY the pilot in command".

 

[luvflyin]

Huh?

14 CFR 91.175(c ) prohibits operating an aircraft below DA unless visibility meets minimums and the "runway environment" is in sight.

It doesn't actually say that. It says you may not "CONTINUE an approach below the authorized DA/DH." Once you make the decision to miss, you are no longer continuing the approach.

 

[flyingron]

I think you're reading too much into that. Generally "continue" on the ILS is more associatiated with a constant path descent (GS), whereas the MDA may be a dive & drive.

No I do not believe I am "reading too much in to it." The words mean what they say and they imply that MDA is a limit but DH is the point where you break off an approach.

Your "read too much into it." In fact, it is completely at odds with the FAA idea of how you're to fly non-precision approaches. They don't believe in dive and drive. The MDA is a hard floor whether you dive down to it or you fly a constant angle descent to it. The DH, is a place where you either continue or you go missed but there is no prohibition to not go below it.

 

[luvflyin]

It doesn't actually say that. It says you may not "CONTINUE an approach below the authorized DA/DH." Once you make the decision to miss, you are no longer continuing the approach.

oops. already covered

 

[AlanM]

Note that the reg actually says "prescribed FOR the pilot in command", not "prescribed BY the pilot in command".

Oops.

Now, here is room for interpretation. WHO is "doing" the "prescribing for"? Can't the PIC prescribe for him/her self what the MDA or DA/DH could be?

 

[RotorAndWing]

Oops.

Now, here is room for interpretation. WHO is "doing" the "prescribing for"? Can't the PIC prescribe for him/her self what the MDA or DA/DH could be?

135/121/125 carriers can specify through OpSpecs various minimums.

 

[aterpster]

135/121/125 carriers can specify through OpSpecs various minimums.

To s point. But, they cannot specify a DA or MDA less than that set forth by source (Part 97). Specials are a different matter.

 

[Kritchlow]

Indeed they are. You are not conversant with TERPs criteria. Not that pilots need be.

Do you have a cite for the 50-foot FAA standard tree? I'd like to learn about it.

Forget about any TERPS or buffer, he's saying the trees protrude into the normal GS on the ILS. obviously this isn't the the case seeing as though every airplane isn't mowing them down.

 

[Kritchlow]

No I do not believe I am "reading too much in to it." The words mean what they say and they imply that MDA is a limit but DH is the point where you break off an approach.

Your "read too much into it." In fact, it is completely at odds with the FAA idea of how you're to fly non-precision approaches. They don't believe in dive and drive. The MDA is a hard floor whether you dive down to it or you fly a constant angle descent to it. The DH, is a place where you either continue or you go missed but there is no prohibition to not go below it.

Actually I believe we are of the same opinion overall.

I do believe a constant glide path is fairly new, and some of the verbiage may not reflect that. I believe many aircraft today are still not equipped for constant glide path.

My point is the phrase "continue" is congruent with a constant glide path, not a dive & drive.

 

[flyingron]

Actually I believe we are of the same opinion overall.

I do believe a constant glide path is fairly new, and some of the verbiage may not reflect that. I believe many aircraft today are still not equipped for constant glide path.

My point is the phrase "continue" is congruent with a constant glide path, not a dive & drive.

So? It still doesn't change the fact that MDA is a hard limit and DH is the point you decide to continue or not an is such NOT a hard limit.

 

[Kritchlow]

So? It still doesn't change the fact that MDA is a hard limit and DH is the point you decide to continue or not an is such NOT a hard limit.

Ahhh, yeah... As I said, we are in agreement on the basics here.

My point earlier was about what I perceived as an incorrect interpretation of "continue". That misunderstanding could have just been poor communication.

 

[aterpster]

Forget about any TERPS or buffer, he's saying the trees protrude into the normal GS on the ILS. obviously this isn't the the case seeing as though every airplane isn't mowing them down.

There is a TERPs thing called the Glideslope Qualification Surface ("GQS") is the reason many airports have LP rather than LPV.

 

[DJTorrente]

There is a TERPs thing called the Glideslope Qualification Surface ("GQS") is the reason many airports have LP rather than LPV.

As to the 50' trees, it was a joke my CFI told (and likely many others) that takeoff and landing are calculated over a 50' obstacle because the FAA mandates all trees be 50' tall. I was also thinking of this incident at Saratoga Springs where the trees had encroached on the glideslope. Admittedly uncommon.

And Dr. House/Rotor/Wing, you play your chosen part to perfection. You are correct, I am not instrument rated. Although I still maintain that if a target tolerance is -0/+100, wisdom advises one to make their actual target +50, ±50. I'm enlightened to learn that -0/+100 applies to non-precision approach MDA, not precision approach decision height.

 

[MauleSkinner]

As to the 50' trees, it was a joke my CFI told (and likely many others) that takeoff and landing are calculated over a 50' obstacle because the FAA mandates all trees be 50' tall. I was also thinking of this incident at Saratoga Springs where the trees had encroached on the glideslope. Admittedly uncommon.

And Dr. House/Rotor/Wing, you play your chosen part to perfection. You are correct, I am not instrument rated. Although I still maintain that if a target tolerance is -0/+100, wisdom advises one to make their actual target +50, ±50. I'm enlightened to learn that -0/+100 applies to non-precision approach MDA, not precision approach decision height.

As a pilot flying in the system, you can adjust your personal minimums upward for whatever purpose, real or imagined, you choose. On the check ride, however, the PTS is quite clear as to nor far you are to descend and what the tolerances are.