4 reds on PAPI - NPA in V/S
Thread Starter
Join Date: Jan 2006
Location: Between a rock and a hard place
Posts: 1,267
Likes: 0
Received 0 Likes
on
0 Posts
4 reds on PAPI - NPA in V/S
During a non-precision approach in vertical speed mode, we have a call "500 Continue/Go-around" which in the SOP manual is defined as G/S +/- 1 dot or on PAPI 3 reds or 3 whites. While still in clouds it's pretty hard to tell, but I was noticing we were drifting slightly low on profile. As we get runway in sight I notice 4 reds on PAPI… and just to be sure call "Go-around". This is my first T/R course, so I am not very familiar with airline ops and heavy machinery just yet. TRE in the back asks why, runway is in sight! Me: "Yes..but, oh well… continue then".
So my question is, what is the general idea among line crew if they find themselves low (4 reds) on a NPA when visual? Go-around or just ease off on the descent rate until intercepting normal profile? What is the recommendation for a LST? At first thought, the answer seemed obvious to me "if in the doubt, go-around" and by the textbook I am outside of the parameters for the "500 continue" call. But when a TRE tells you differently it leaves me somewhat confused. I am not completely new to aviation, have about 2000 hrs of instructing so I know it's not an exact science, there are many opinions out there… so more looking for "general (maybe average?) opinion" and, as I said, what do to to satisfy the TRE on a skill test?
Thanks in advance for your help
PS. Just to add, "500 continue" is on top of the regular landing gate at 1000 ft IMC, which is less specific in vertical deviation from profile. Just says "should be on vertical profile".
So my question is, what is the general idea among line crew if they find themselves low (4 reds) on a NPA when visual? Go-around or just ease off on the descent rate until intercepting normal profile? What is the recommendation for a LST? At first thought, the answer seemed obvious to me "if in the doubt, go-around" and by the textbook I am outside of the parameters for the "500 continue" call. But when a TRE tells you differently it leaves me somewhat confused. I am not completely new to aviation, have about 2000 hrs of instructing so I know it's not an exact science, there are many opinions out there… so more looking for "general (maybe average?) opinion" and, as I said, what do to to satisfy the TRE on a skill test?
Thanks in advance for your help
PS. Just to add, "500 continue" is on top of the regular landing gate at 1000 ft IMC, which is less specific in vertical deviation from profile. Just says "should be on vertical profile".
Join Date: Aug 2011
Location: far too low
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
On a lst (especially your first one) you will never fail for electing to go around. Choosing to land in the sim when your ops manual tells you to bin the approach, will leave you in a world of trouble. Obviously you can't go around forever but in this case I think you were right.
Thread Starter
Join Date: Jan 2006
Location: Between a rock and a hard place
Posts: 1,267
Likes: 0
Received 0 Likes
on
0 Posts
What did your TRI say?
Join Date: Dec 2003
Location: England
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
Hi 172,
PAPI: Precision Approach Path Indicator
NPA: Non-Precision Approach.
PAPI's may not always be set to the same angle as the NPA in use and dependent on your a/c type, may also not be set for your eyeline.
So, as part of the brief, you need to check a) the PAPI slope and b) if / where the lateral track of the NPA intercepts the RCL.
With the exception of a no-go-below altitude, the tolerance is +/- 100' for a NPA vertical profile. Assuming you have maintained this correctly down the approach and you are stable at your relevant SOP'd gate, then you MAY NOT BE INTERCEPTING THE PAPI's. A NPA, by definition, is not as precise as an ILS or approach flown on PAPI's / VASI's.
Once visual, especially with a transition close to minima, dont rush the decision; let your mental model adjust. Check the ROD is sensible (usually c.700fpm for 3 degrees GS dependant), how did the final altitude check against actual a/c alt? If all is good, gently adjust onto the PAPI's (if they are there). At 200' you will have an idea if the approach is going to work or not. 4 whites at 200' is a good clue to GA!
DA is not a decision to land (hence your SOP wording), it is a decision to CONTINUE THE APPROACH assuming stable criteria are still being met. Your stable criteria from your ops manual appear not to be too helpful with regard to NPA's. I would assume +/- 1 dot as +/- 100' in this case.
Hope that helps. If you have any questions PM me.
PAPI: Precision Approach Path Indicator
NPA: Non-Precision Approach.
PAPI's may not always be set to the same angle as the NPA in use and dependent on your a/c type, may also not be set for your eyeline.
So, as part of the brief, you need to check a) the PAPI slope and b) if / where the lateral track of the NPA intercepts the RCL.
With the exception of a no-go-below altitude, the tolerance is +/- 100' for a NPA vertical profile. Assuming you have maintained this correctly down the approach and you are stable at your relevant SOP'd gate, then you MAY NOT BE INTERCEPTING THE PAPI's. A NPA, by definition, is not as precise as an ILS or approach flown on PAPI's / VASI's.
Once visual, especially with a transition close to minima, dont rush the decision; let your mental model adjust. Check the ROD is sensible (usually c.700fpm for 3 degrees GS dependant), how did the final altitude check against actual a/c alt? If all is good, gently adjust onto the PAPI's (if they are there). At 200' you will have an idea if the approach is going to work or not. 4 whites at 200' is a good clue to GA!
DA is not a decision to land (hence your SOP wording), it is a decision to CONTINUE THE APPROACH assuming stable criteria are still being met. Your stable criteria from your ops manual appear not to be too helpful with regard to NPA's. I would assume +/- 1 dot as +/- 100' in this case.
Hope that helps. If you have any questions PM me.
Thread Starter
Join Date: Jan 2006
Location: Between a rock and a hard place
Posts: 1,267
Likes: 0
Received 0 Likes
on
0 Posts
Thanks all for the time taken to reply to my question.
Our stabilized approach criteria seem to be copy & paste of FCTM. The +/- 1 dot seem just to be to pass the "500 continue" call whereas the stabilized definition is more along the lines of "on the correct vertical path", which is more vague. In the particular case above the V/S profile matched the ILS profile, however we were low on the last altitude vs. DME check but correcting so the actual ROD was benign.. if I recall correctly set to 700 fpm. The end result was an uneventful landing in the TDZ.
Btw, what is your take on winding down the V/S thumbwheel 0,5 nm before the actual descent point on a V/S NPA? That was the idea of one TRI, which has the advantage of being on profile as the descent is established. Another TRI was of the opinion it was a bust of platform altitude, instead we have to "chase" the profile with slightly higher ROD initially.
Our stabilized approach criteria seem to be copy & paste of FCTM. The +/- 1 dot seem just to be to pass the "500 continue" call whereas the stabilized definition is more along the lines of "on the correct vertical path", which is more vague. In the particular case above the V/S profile matched the ILS profile, however we were low on the last altitude vs. DME check but correcting so the actual ROD was benign.. if I recall correctly set to 700 fpm. The end result was an uneventful landing in the TDZ.
Btw, what is your take on winding down the V/S thumbwheel 0,5 nm before the actual descent point on a V/S NPA? That was the idea of one TRI, which has the advantage of being on profile as the descent is established. Another TRI was of the opinion it was a bust of platform altitude, instead we have to "chase" the profile with slightly higher ROD initially.
Join Date: Mar 2007
Location: Birmingha,
Age: 40
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
If you're at the company I think you're at then your OM A deals with this. 8.3.0.3.11.2 - under point 4 it deals with profile deviations below the landing gate. A GA would only be mandatory if you do not believe touchdown will be within the TDZ. So 4 reds is not necessarily a GA once below the landing gate. Whether or not a GA is sensible in that scenario is another matter.
Guest
Posts: n/a
Leaving aside weather and classification of the approach, you need to know which aircraft type was used to set up the PAPI.
An [MEHT] minimum eye height above the threshold is a key factor in ensuring a safe approach following the the guidance of the PAPI. If that design a/c is a B747 or A340-600 then clearly in a smaller aircraft your wheels will be higher if your eyes are following the lights.
An [MEHT] minimum eye height above the threshold is a key factor in ensuring a safe approach following the the guidance of the PAPI. If that design a/c is a B747 or A340-600 then clearly in a smaller aircraft your wheels will be higher if your eyes are following the lights.
Thread Starter
Join Date: Jan 2006
Location: Between a rock and a hard place
Posts: 1,267
Likes: 0
Received 0 Likes
on
0 Posts
ast83, there are obviously multiple manuals that deal with the scenario and they are all up for interpretation, e.g. OM-A says about Go-around:
A Go-Around shall also be made:
- If the success of the approach becomes doubtful, e.g. approach not stabilised by 500 ft AAL (300 ft AAL after circling), required elements of the landing threshold not clearly identified, etc.
or...
- If below 1,000 ft AAL, any significant departure from the normal approach path occurs and corrective action is not immediately effective.
(my bold)
I guess for a checkride you'd be home safe if you applied it conservatively.
A Go-Around shall also be made:
- If the success of the approach becomes doubtful, e.g. approach not stabilised by 500 ft AAL (300 ft AAL after circling), required elements of the landing threshold not clearly identified, etc.
or...
- If below 1,000 ft AAL, any significant departure from the normal approach path occurs and corrective action is not immediately effective.
(my bold)
I guess for a checkride you'd be home safe if you applied it conservatively.
Join Date: Mar 2007
Location: Birmingha,
Age: 40
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
172driver, quite right about the checkride. I always tell our cadets you cannot fail any check for going around when you could have continued. Continue when you should have gone around however is not so good. However I can assure you that once inside the gate, company procedures do not mandate a GA solely because you dip into 4 reds ( or whites ). I would add that I don't find your instructors reasoning that just because runway was in sight you could have continued, particularly helpful. Ultimately it is a judgement call, and remember a lot of time and effort has gone into the wording of those manuals to ensure they are very much open to interpretation!
My view is, do what your manuals say.
If the manuals are unclear though, understand why we have a stabilized approach. The idea is that from a certain altitude the aircraft must be fully configured, on profile, and on centerline, and most importantly, only require minor deviations in power and flight path to achieve a landing.
With that said, in your scenario I would make an assessment of the situation and decide whether I think it can be fixed by making a minor adjustment to the profile (did the papi only just go four reds or is the runway up near the top of the windscreen?) If I think it can be saved I'd call "correcting" and attempt to save it. If it became apparent that a minor correction would not be enough or if I thought it couldn't be saved I'd go around.
I agree with the general sentiment that if in doubt you're better off going around than continuing an approach you're not comfortable with.
Something else to consider with an NPA is that you have to expect to do some maneuvering when you get visual simply because the approach is not very accurate. If you have four reds at the point you get visual but you haven't descended below MDA yet I'd make corrections and reassess at the MDA.
If the manuals are unclear though, understand why we have a stabilized approach. The idea is that from a certain altitude the aircraft must be fully configured, on profile, and on centerline, and most importantly, only require minor deviations in power and flight path to achieve a landing.
With that said, in your scenario I would make an assessment of the situation and decide whether I think it can be fixed by making a minor adjustment to the profile (did the papi only just go four reds or is the runway up near the top of the windscreen?) If I think it can be saved I'd call "correcting" and attempt to save it. If it became apparent that a minor correction would not be enough or if I thought it couldn't be saved I'd go around.
I agree with the general sentiment that if in doubt you're better off going around than continuing an approach you're not comfortable with.
Something else to consider with an NPA is that you have to expect to do some maneuvering when you get visual simply because the approach is not very accurate. If you have four reds at the point you get visual but you haven't descended below MDA yet I'd make corrections and reassess at the MDA.
3 issues here.
PAPI may not be set for your aircraft. For every foot the MEHT for the PAPI is over your aircraft eye height, you'll land 7 meters long. Thus, you could be flying an A320 one dot low on a runway that takes a380s etc. to be closer to correct slope upon which your landing performance is predicated.
Second, not sure what aircraft type you are referring to but from my Airbus FCTM
Note, the go around is if you can't get stable again....
Finally, as for hitting the the FPA before the FAF. Same FCTM instructs to do it 0.2nm before....
PAPI may not be set for your aircraft. For every foot the MEHT for the PAPI is over your aircraft eye height, you'll land 7 meters long. Thus, you could be flying an A320 one dot low on a runway that takes a380s etc. to be closer to correct slope upon which your landing performance is predicated.
Second, not sure what aircraft type you are referring to but from my Airbus FCTM
Take immediate corrective action to control the exceeded parameter back into the defined stabilized conditions
Assess whether stabilized conditions will be recovered early enough prior to landing, otherwise initiate a go-around
Assess whether stabilized conditions will be recovered early enough prior to landing, otherwise initiate a go-around
Finally, as for hitting the the FPA before the FAF. Same FCTM instructs to do it 0.2nm before....
Join Date: Aug 2001
Location: BFS
Posts: 1,177
Likes: 0
Received 0 Likes
on
0 Posts
Maybe another point to consider, though it may just confuse the issue.
On a lot of NPA's you may not be lined up with the landing runway until the MAP. Therefore as alluded to above the validity of the PAPI's may be questionable.
However you mention that you were drifting below profile, so in this case I doubt very much you could be faulted.
On a lot of NPA's you may not be lined up with the landing runway until the MAP. Therefore as alluded to above the validity of the PAPI's may be questionable.
However you mention that you were drifting below profile, so in this case I doubt very much you could be faulted.
Thread Starter
Join Date: Jan 2006
Location: Between a rock and a hard place
Posts: 1,267
Likes: 0
Received 0 Likes
on
0 Posts
Thanks again for the discussion, I was just interested to see what the general opinion was among more experienced pilots. From the visual judgement, we weren't far off the PAPI and it felt like and easy correction could be made to get back onto profile. I was mostly wondering if 4 reds below the landing gate would be an automatic disqualifier of the approach. My conclusion would be, in the real world, the answer is not black & white and it just depends.
