Instrument Approaches with failures
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Instrument Approaches with failures
A question put to me earlier by a friend of mine, pre his IR test.
You are on an ILS DME approach, you then lose your glideslope, Do you go round or do you continue Loc only ?
3 people asked (me one of them) , 3 different answers came out.
LEGALLY where can the answer be found ?
What is the correct answer ?
V.
You are on an ILS DME approach, you then lose your glideslope, Do you go round or do you continue Loc only ?
3 people asked (me one of them) , 3 different answers came out.
LEGALLY where can the answer be found ?
What is the correct answer ?
V.
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The answer depends on the situational awareness and skill of the pilot, for a beginner I would say that the safe option is to go around.
Provided you're skilled enough and the "loc" (or "loc+dme") approach is described on the chart you're using, you can continue this "downgraded" approach (without descending lower than the correct MDH/A of course!).
Provided you're skilled enough and the "loc" (or "loc+dme") approach is described on the chart you're using, you can continue this "downgraded" approach (without descending lower than the correct MDH/A of course!).
Last edited by FredFri; 23rd Mar 2007 at 07:03.
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There is real world, and there is checkride. Real world, unless I'm very low on fuel, I'm going missed, get clearance for another approach, rebrief for the new approach, and then fly it. For a checkride, or if I'm really worried about fuel (flying a 412), then I may continue, depending on the weather, my situational awareness, my confidence in my SIC, and many other factors. It's certainly legal to continue, using the localizer minima, and I don't think that is spelled out anywhere. Whatever is not prohibited is legal, at least in the US, and as long as you have a clearance for an approach and don't descend below the minimum altitude for the approach, and can fix the MAP properly, then you're legal to fly the approach. Legal and safe are not necessarily the same, however, so I would prefer to rebrief and start the approach over. I don't think it's possible for the examiner to fail the applicant for doing this, nor do I think he should be failed for continuing, assuming no minima were broken.
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I would continue because as a professional I've thought about this in the slack time on the way in and have the plate ready. Do not assume that you are going to get in on the first run! It depends also on the country you're in - in Canada, they would be very much looking for a real world approach, even on a check ride. In an airline, the commercial department will love you if you keep overshooting and unnecessarily wasting fuel.
phil
phil
An Air Methods EMS crew reverted to a Localizer approach at Bluefield, West Virginia once upon a time. The approach at that time was very unusual in that it did not have a locator outer marker (LOM) and relied upon radar vectoring.
The crew distinctly asked ATC for a vector that would take them well outside the glide slope interception point but for some reason still found themselves unable to obtain the glide slope indication following an early turn-in vector by ATC.
They probably assumed an instrument or system failure and proceeded with the Localizer approach.
The hit a mountain on the far side of the airport at approximately the MDA and killed all four aboard the Bell 412.
There were a host of other issues surrounding that crash that went unremarked about during the investigation thus one cannot put it down to a "simple" crew failure.
The point to be remembered.....if you do not know without doubt why you have no glide slope.....GO AROUND! Do so early...do so whenever any ambiguity occurs. No one got killed climbing away from the ground and returning for another approach. Damn the commercial department....it is your hide that will be plastered to the Smoke House Door if you encounter the Earth at a most in-opportune time.
The DME was not in the "Hold" position as it should have been if they had been using the on-field Vortac for DME mileage readouts and the Loran/GPS was not set to the airfield coordinates for assistance in Situational Awareness. The aircraft was the company spare which had been flown in by the Corporate Check Airman. The Crew had done a bag drag from their normal duty aircraft to the spare and departed on a flight they had turned down earlier in the day due to the inclement weather. With the Check Airman on site, they may have felt pressured to make the IFR flight despite having refused earlier.
The Captain of the aircraft was the Base Manager, Training Captain, and Safety Officer.
The crew distinctly asked ATC for a vector that would take them well outside the glide slope interception point but for some reason still found themselves unable to obtain the glide slope indication following an early turn-in vector by ATC.
They probably assumed an instrument or system failure and proceeded with the Localizer approach.
The hit a mountain on the far side of the airport at approximately the MDA and killed all four aboard the Bell 412.
There were a host of other issues surrounding that crash that went unremarked about during the investigation thus one cannot put it down to a "simple" crew failure.
The point to be remembered.....if you do not know without doubt why you have no glide slope.....GO AROUND! Do so early...do so whenever any ambiguity occurs. No one got killed climbing away from the ground and returning for another approach. Damn the commercial department....it is your hide that will be plastered to the Smoke House Door if you encounter the Earth at a most in-opportune time.
The DME was not in the "Hold" position as it should have been if they had been using the on-field Vortac for DME mileage readouts and the Loran/GPS was not set to the airfield coordinates for assistance in Situational Awareness. The aircraft was the company spare which had been flown in by the Corporate Check Airman. The Crew had done a bag drag from their normal duty aircraft to the spare and departed on a flight they had turned down earlier in the day due to the inclement weather. With the Check Airman on site, they may have felt pressured to make the IFR flight despite having refused earlier.
The Captain of the aircraft was the Base Manager, Training Captain, and Safety Officer.
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Always know your min-safe altitude
To go around or not???? There is no correct single answer to your question, it depends where you are on the approach. Always ask you self two things: 1. Where am I? (requires good SA) 2. Where am I safe? (i.e. min safe alt, step down alt, etc.)
Back to your question. As a professional IFR pilot, of course you briefed this eventuality in your approach brief. (it is alway easier to make this decision prior to starting the appoach, that is why it is good to pre-brief loss of glide slope so your crew is clear on the plan of action.)
If you are at or above a step down altitude for the segement of the LOC ONLY approach then either level off or descend to the appropriate altitude and continue with the LOC ONLY. If you are below the level of step down altitude (for the segment being flown) then immediately initiate a climb to a safe altitude. From there you can determine if the approach is still effective and determine the best course of action.
If you have not pre-briefed the loss of glideslope event, then it may be best to just initiate a climb, or level at a safe altitude, and commence the missed approach. But... remember that obstacle clearance for the missed approach segment is predicated on commencing the missed approach AT THE MISSED APPOACH POINT. Ergo it is best to fly the LOC to that point (at a safe altitude) and commence the missed approach from there. Of course if at any time ATC puts you on a vector they are now responsible for your obstacle clearance.
When in doubt go into the missed, re-brief and try it again. Better to be a little late, burn more gas, and bring the aricraft, crew & pax home safe then try to be the hero in the Chief Pilots eyes. The last thing that you should be thinking about after you have had an EQUIPMENT FAILURE is what the Chief Pilot is going to say.
Back to your question. As a professional IFR pilot, of course you briefed this eventuality in your approach brief. (it is alway easier to make this decision prior to starting the appoach, that is why it is good to pre-brief loss of glide slope so your crew is clear on the plan of action.)
If you are at or above a step down altitude for the segement of the LOC ONLY approach then either level off or descend to the appropriate altitude and continue with the LOC ONLY. If you are below the level of step down altitude (for the segment being flown) then immediately initiate a climb to a safe altitude. From there you can determine if the approach is still effective and determine the best course of action.
If you have not pre-briefed the loss of glideslope event, then it may be best to just initiate a climb, or level at a safe altitude, and commence the missed approach. But... remember that obstacle clearance for the missed approach segment is predicated on commencing the missed approach AT THE MISSED APPOACH POINT. Ergo it is best to fly the LOC to that point (at a safe altitude) and commence the missed approach from there. Of course if at any time ATC puts you on a vector they are now responsible for your obstacle clearance.
When in doubt go into the missed, re-brief and try it again. Better to be a little late, burn more gas, and bring the aricraft, crew & pax home safe then try to be the hero in the Chief Pilots eyes. The last thing that you should be thinking about after you have had an EQUIPMENT FAILURE is what the Chief Pilot is going to say.
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Approach Briefs!
Looking at the quote, there is only one answer.
800
You are on an ILS DME approach, you then lose your glideslope,
You are on the approach and then loose your glideslope. This indicates that you have already established the approach and the aid (either on the ground or in the aircraft) has become unservicable OR is out of tollerance. This then requires a missed approach. As mentioned previously; maintain safe height and fly to the missed approach point (fix) prior to starting the missed approach procedure. But, you would already know all that, because that is what you briefed in your approach brief - didn't you!
800
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Good points, Bigkahuna and 800 - of course, it isn't entirely black and white - I was trying to make the point that the possibility should have been thought about first - but not very clearly! Of course, if you are unsure, go around, and remember that the holding pattern is your friend while you get your head clear. There is a fine line between keeping the company happy and staying alive, and you should always of course opt for the latter!
phil
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In JAA land, presumably other authorities would be similar, if you go-around once the failure occurs you are safely dealing with the issue and reducing the risk involved by getting away from mother earth. This would give you time to choose a suitable non-precision approach and position and brief appropriately. I would be very surprised if an examiner could fail a candidate for choosing the apparent safe option, I could be wrong and standby to be corrected.
Certainly on my OPC's if you are half scale or more on either LOC or GS then it's an immediate go-around. Therefore if either failed half-way down the approach I would treat this in the same manner. After all when the glideslope fails it defaults past half-scale deflection. I would therefore make the same correction as if I had drifted past half-scale by inaccurate flying. The result would of course be the same: go-around.
This hopefully will help, just my thoughts on the subject.
Good luck to the candidate in question.
H
PS: Vee, do I know them?
Certainly on my OPC's if you are half scale or more on either LOC or GS then it's an immediate go-around. Therefore if either failed half-way down the approach I would treat this in the same manner. After all when the glideslope fails it defaults past half-scale deflection. I would therefore make the same correction as if I had drifted past half-scale by inaccurate flying. The result would of course be the same: go-around.
This hopefully will help, just my thoughts on the subject.
Good luck to the candidate in question.
H
PS: Vee, do I know them?
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Mmmmm......
If your approach plate has printed on it "Loc Out Minima" and you have briefed for that in the event of a GS failure ABOVE the Localiser minima you may continue the approach to the "Loc Only" minima. That is after all why those minima are included in the ILS approach plate.
If you only have minima for the ILS approach and the GS fails then you MUST fly the missed approach procedure if at the time of the failure you are in IMC .... obviously if you are in VMC you may continue the approach visually.
It is probably wise to be aware that you can convert that approach .... there is an arguement to be made that in a helicopter unless you are carrying alot of alternate fuel you might be putting an aircraft at risk by going missed approach unneccesarily and end up having to declare a fuel emergency. I know it should not happen but the realities mean it may (ie say flying IMC in a Bk117 which ain't got the best endurance in the world?).
Cheers
If your approach plate has printed on it "Loc Out Minima" and you have briefed for that in the event of a GS failure ABOVE the Localiser minima you may continue the approach to the "Loc Only" minima. That is after all why those minima are included in the ILS approach plate.
If you only have minima for the ILS approach and the GS fails then you MUST fly the missed approach procedure if at the time of the failure you are in IMC .... obviously if you are in VMC you may continue the approach visually.
It is probably wise to be aware that you can convert that approach .... there is an arguement to be made that in a helicopter unless you are carrying alot of alternate fuel you might be putting an aircraft at risk by going missed approach unneccesarily and end up having to declare a fuel emergency. I know it should not happen but the realities mean it may (ie say flying IMC in a Bk117 which ain't got the best endurance in the world?).
Cheers
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I sat an Instrument Rating test in India many years ago. The glide slope was lost and I went around, continued with the test. During the debrief the examiner asked if I had considered converting the the approach to a localiser only approach. It was my first ever rating so I was rather nervous and the thought never crossed my mind. I of course replied no and was told that both going around or converting the approach were correct if the localiser only was listed and briefed.
The examiner was from the Dutch RLD.
I believe therefore you can switch if briefing carried out during initial brief.
The examiner was from the Dutch RLD.
I believe therefore you can switch if briefing carried out during initial brief.
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Like most aviation answers, it depends.
Before starting the approach you should have an idea of what the weather is.
If the approach has a localizer only minimum-which most do then( assuming the ILS has been properly tuned and identified and you don't have a VOR frequency tuned in -which has happened, more than once): check the locailizer flag, check the F/O HSI if no flags then continue to loaclizer only minimums. IF BELOW LOCALIZER ONLY MINIMUMS then a missed approach must be executed.
On ILS approaches I brief the ILS DH and the LOC only MDA or NDB which ever may apply, with the expectation of continuing on to LOC minimums if the GS is lost.
One airport I flew into regularly had seasonal problems with the GS when in the spring the snow melted during the daytime and then the water froze at night causing havok with the GS transmitter.
In any event its no big deal-unless the weather is 200 with an RVR of 1200 ft (400 METERS).
Before starting the approach you should have an idea of what the weather is.
If the approach has a localizer only minimum-which most do then( assuming the ILS has been properly tuned and identified and you don't have a VOR frequency tuned in -which has happened, more than once): check the locailizer flag, check the F/O HSI if no flags then continue to loaclizer only minimums. IF BELOW LOCALIZER ONLY MINIMUMS then a missed approach must be executed.
On ILS approaches I brief the ILS DH and the LOC only MDA or NDB which ever may apply, with the expectation of continuing on to LOC minimums if the GS is lost.
One airport I flew into regularly had seasonal problems with the GS when in the spring the snow melted during the daytime and then the water froze at night causing havok with the GS transmitter.
In any event its no big deal-unless the weather is 200 with an RVR of 1200 ft (400 METERS).
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ILS/DME approach
Pilots,
When executing ILS/DME approach, DME because there are no markers, what do you pilots intend to do in case of DME failure. Will you go around immediately or you will continue ILS approach till DA/H?
Regards,
When executing ILS/DME approach, DME because there are no markers, what do you pilots intend to do in case of DME failure. Will you go around immediately or you will continue ILS approach till DA/H?
Regards,
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DME is not required for an ILS approach
Also for the "legal" point of view I believe that you need three things for a approach to be a precision approach :
- axis indication (loc)
- slope indication (glide)
- and a distance information "with an accuracy of at least +/- 0.5 NM"
This indication had been for long provided by the markers which tend to become "old stuff", the newer and more precise DME is now the norm.
For the reference, it should be somewhere in the ICAO Publications (document 8168 - Procedures for Air Navigation Services: Aircraft Operations - Volume II: Construction of Visual and Instrument Flight Procedures)
And yes Gomer, I know I didn't answer what shall be done in the situation described
Last edited by FredFri; 25th Mar 2007 at 21:51.
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In the US, the only use for DME in conjunction with an ILS approach is to fix the OM, if necessary for that. Subsequently, it is only for situational awareness. The MAP is DA, on the GS. If you have already fixed the OM on the approach, then you have no further legal need for DME. It could be useful under many circumstances, but it's not required. What is legal across the pond I don't know.
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FredFri:
There is no distance (DME) requirement for ILS approaches in Canada.
The Middle and Outer Marker beacons has been decomissioned [here] for over 10 years.
The majority of ILS approaches don't have DME, but the majority do have an NDB as the Final Approach Fix (FAF)-usually about 4.5 to 5 nm from the threshold.
A decent to localizer ONLY minimums (in the event of GS failure) would be done on timing from the FAF, i.e.cross the beacon start the time , decend down to the LOC MDA, wait for the timing which corresponds to your ground speed, if nothing is seen at the end of time-Missed Approach.
Some ILS approaches have no fixes but require RADAR vectors to determine the IB Course , there are a couple of examples of these at YYZ .
There is no distance (DME) requirement for ILS approaches in Canada.
The Middle and Outer Marker beacons has been decomissioned [here] for over 10 years.
The majority of ILS approaches don't have DME, but the majority do have an NDB as the Final Approach Fix (FAF)-usually about 4.5 to 5 nm from the threshold.
A decent to localizer ONLY minimums (in the event of GS failure) would be done on timing from the FAF, i.e.cross the beacon start the time , decend down to the LOC MDA, wait for the timing which corresponds to your ground speed, if nothing is seen at the end of time-Missed Approach.
Some ILS approaches have no fixes but require RADAR vectors to determine the IB Course , there are a couple of examples of these at YYZ .
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the majority do have an NDB as the Final Approach Fix (FAF)-usually about 4.5 to 5 nm from the threshold
Looking at many ILS approach charts, you'll find that somewhere between 4 and 5 nm from threshold there is an OM or a DME info or a NDB.
Anything that complies with the accuracy needed by the ICAO definition of a precision approach (I gave the reference to show it's not only a view from this side of the pond
).There may be ILS approaches without that info on final but if there are I would guess that the DH must be higher than the usual 200ft.
Last edited by FredFri; 26th Mar 2007 at 06:19.
legally speaking, you were cleared to execute the ils not the loc approach.
How many of us brief the missed approach procedures prior to the start of the approach as a standard procedure?
How many of us begin an approach fully prepared physically....mentally....to do that missed approach or do we happily trundle down the approach with a mindset that we shall always break out and land?
How many of us begin an approach fully prepared physically....mentally....to do that missed approach or do we happily trundle down the approach with a mindset that we shall always break out and land?