What happens if you fly the ILS and it goes wrong?
 

What happens for instance if the ILS signal disappears whilst you are flying an approach or if you fly the ILS more than half scale deflection. Is it normal to maintain heading and then a go around before reaching DA?

The gadget is giving you a clue where you are .. in amongst the rocks and other hard things.

(a) if the signal fails, you don't want to be there ... unless you can revert to another procedure (with all that that entails) would you not want to do the miss without delay (but with the caveat that one needs to follow the procedure splays for protection) ?

(b) if you are outside a tight tracking tolerance, then that didn't occur suddenly and the pilot should be aware of what was happening. Either get back into the crossed needles without delay or think about (a)

G/A for sure. If you have been smart you have tuned a marker beacon or VOR and have an RMI needle showing it so that you can track in the right direction.:ok:

PP

If you are visual with the RWY: Continue visually. Don't forget to tell ATC
If you are in IMC: GO-AROUND.

thanks for the replies! But imagine if you lost the loc or it went full scale, what would you do then, as you may be just about to go around into a hill etc:\ - imagine say they didnt have an NDB on the airfield

...errr....you go around or continue visually as stated previously. A go around is a normal maneuvre and therefore if the published procedure is flown correctly, one will not crash into terrain. If the airfield doesn't have an NDB, the procedure may be based on another navaid, or just be something along the lines of climb to 3000' on runway heading.

No you dont understand. If you are off the localiser by full scale deflection and presuming the airfield is in a valley or theres high terrain you are therefore outside the normal approach and a go around in this situation could still be dangerous.

We don't fly down the glideslope at full scale deflection :rolleyes:
and if you are on the ILS and the signal fails you know where you are and you Go Around from there and follow the MAP.

... but how/why have you permitted the FS LLZ deflection without having already done something appropriate about it ? One doesn't just suddenly become FSD and, at the end of the day, it is not rocket science to pedal one's way down the ILS with crossed needles.

However, if one were in such a situation, there are more hazards to be had continuing rather than aborting so the preferred option would be to miss and turn towards the LLZ during the initial climb.

That's why with approaches/departures at airports surrounded with mountains you put ''Terrain on ND'' on, in the Airbus'. In other types wich do not have such feature, weather radar returns from the mountains may help...

May I remind you that such airports have very strict MSA's and radar vectoring altitudes. Also there might be an instructon not to arm the approach outside a certain distance of the localizer due false returns of the mountains.

Used to get a fair number of these problems at Heathrow long ago. Crews would report the ILS had failed so we'd go straight into SRAs until they became visual. I don't know how many ILS-equipped airfields have radar but suspect an SRA would be the standard alternative at those that are...

SRA’s? there is a blast from the past.......sadly fewer and fewer civil ATC units are able to offer an SRA or PAR today HD.
I understand that the cost in training and currency is considered prohibitive, considering the rise of GPS/ RNAV etc and the decreasing need for such a service at civil airfields.
Pity really, they were the ultimate in co-ordination & co-operation long before CRM was even considered….

machlimter99 - the point being that you shouldn't be full deflection in the first place. If you are getting out of tolerances you G/A and try again.
Normally should the ILS for some reason stop radiating you will at that precise moment be on the LOC and G/S and therefore are going around from a known position. Hopefully you will either have suitable Nav aids or GPS feed to an FMC to fly the required profile. If not, then realistically you will either receive positive radar control from ATC, or if that is also not available you fly a combination of old fashion dead reckoning.
Do take note that when an approach is being constructed all of this is considered....

A general point here that hasn't been made so far. Every approach should be made with the expectation that you will NOT be able to land off it and that you may have to go-around. To that end the Missed Approach Procedure (MAP) should form part of your approach briefing, and should be covered considering both the lateral and vertical profiles, and also how you actually fly your aircraft.

To return to your example: If the needles have gone full scale deflection, and the ILS is still working then NO you should not continue on your heading. It was this heading that has gotten you off the ILS in first place! Depending on how far out you are you should try to recover the ILS. If in doubt go around doing your best to recover the published MAP.

In your example of steep valleys. I presume you are talking of a hypothetical situation, and I can only echo the advice given by others here, brief thoroughly, and fly accurately. If the ILS itself fails then go-around advise ATC and ask for any assistance they can give you via radar.

Pretty much my views, but if the ILS goes full-scale aren't you required to G/A? Maybe I'm thinking about the Instrument Checkride where you fail if you get full-deflection :p

machlimiter99
The situation you are trying to describe generally doesn't exist. Long before the needle got to full scale the PF would have taken action to restore the correct track. LLZ needles don't just suddenly go from centred to full scale- assuming the equipment is working correctly- they drift,slowly, as the aeroplane deviates from the required track. On autocoupled approach the autopilot reacts that in fractions of a second. Manual approach maybe a bit longer. So unless some major event has occured to suddenly push or direct the aircraft rapidly to one side, it just isn't going to happen.

I would certainly advocate the Go-Around is the safest option.

Your question(s) have broadly been what to do? And how to do it? In answer to the first part Go-Around. In answer to the second part make every effort using all available aids to fly the MAP both laterally and vertically.

If you have a particular airfield in mind then I am sure that if you ask someone on this forum will be able to give you more specific advice.

There's been a lot of commonsense replies so far and I shall attempt to provide a bit more.

First, I'm not even going to contemplate how any pilot could allow such a sustained tracking error that FSD on the LLZ would be achieved without some sort of corrective action - heading change in the early stages, while it's still viable, or an immediate go-around before it becomes unviable. Any pilot who can allow such a situation to develop, whether manually or by ignoring a possible foul-up in the automatics, is not the sort of pilot who should be in a cockpit.

Second, while I can't imagine such a situation, if the LLZ suddenly went to FSD, I'd already have a fair idea of how I was tracking immediately prior to that event. If I was on the LLZ, it's a fair bet that my heading was appropriate so I'd stick with that while initiating the G/A and climbing for all that my aeroplane is worth. If I wasn't actually on the LLZ, at least I'd be within my tracking tolerance and, depending on circumstances, might make a slight, strategic heading change while initiating the G/A and, once again, climbing at the maximum safe limit.

If your next question is... how do I identify the point where the missed approach should start? Well that's a good question and the way in which a pilot handles it is part of the reason why you get paid the big bucks! Of course, the DA is the point of commencement of the missed approach, so you need to think about the ways in which you might identify it. Sometimes, there'll be an Inner Marker, or a published DME distance - or at least a way to identify that DME distance. As my aircraft is equipped with a TSO C-129a GPS, I'd already have the RWY THR position selected on it, if it's in the database. If all else fails... well, what can I say? You need to exercise your own best guess as to the location of the point that equates to DA, as a distance from the THR. There again, you're being paid to exercise command judgement that is intended to keep your pax safe.

<<SRA’s? there is a blast from the past.......sadly fewer and fewer civil ATC units are able to offer an SRA or PAR today HD.
I understand that the cost in training and currency is considered prohibitive,>>

Not wholly so in the UK. Although PAR is long gone at the majority of civil airfields, I suspect that every airfield with surveillance radar can offer SRAs; certainly all the major ones can. SRAs are part of normal training for radar controllers at airfields and there is a requirement for them to maintain proficiency with regular practice. Fear not, if the ILS fails some kind gent/gentess will gabble you down the approach!

SRAs at London airports
 

HD,

You're right - after last Summer's bash of Northern Runway Ops at LGW, all the guys & gals at TC were fully up to speed, 50 or so a night for 60 or more nights, sometimes in marginal wx conditions. Occasionally the controllers seemed able to handle 2 or 3 at once, really clever stuff!


Cheers,
TheOddOne

Thanks for the replies. Would you continue in level flight until the MAP or start a climb straight away- after youve had FSD or the signal has failed??