When To Arm The Automation When Shooting an ILS
 

When flying an ILS, I have always been taught (and practise this too) to arm the Automation for the ILS, (FND in an EC225 & believe its called different things in different machines) as soon as I am established on the localiser and clear for the approach. Then I just monitor and do whatever else I need to do

However someone I was speaking to who just came back from a 139 Initial told me he was specifically told to arm the FND (or 139 Equivalent) at the exact moment he intercepts the Glideslope, and not a second before. Surely if you got distracted for whatever reason you would then find yourself above the glideslope?

I personally feel better arming it before intercepting for various reasons, as long as Im established and cleared by ATC.

However I am wondering if the practice mentioned above is something specific to 139's or if anyone else does this? I'm not saying the method I use is the only method and the best etc, but just more curious for reasons why some are taught to arm only at the exact moment of intercepting the glideslope, for my own knowledge and all.

Thanks in advance

I arm it when I have been turned onto the intercepting heading and have been 'cleared for the ILS'. This allows the aircraft to intercept the localiser itself, with the two of us monitoring it.

On the closing heading, when told to "call established"


SND

So would there be ant good reason instructors teaching students to arm it at the exact point of intercepting the glide slope and not a second before?

I can't think of one.

Yes definitely when on an intercept heading and cleared for the approach. Unless there is some strange quirk of the AW139 (we need Geoffers to tell us) the practice of having to arm it at a precise moment seems bonkers.


This may be a facet of the fact that someone with no experience of operating the type (or maybe any similar type) can be a sim instructor.

The system is designed to intercept the LOC and GS, it probably cost a fortune, why on earth does the pilot have to do the work???

Arm it when you are within 90 degrees of the inbound heading, normally on the base turn. As for the glide slope, you'll normally capture the glide slope from below anyway so if it's an independent button from the localiser you can arm that anytime (as long as you're not flying on the outbound leg away from the ILS or you will end up in space!). Engage both together if they are independent on your base turn.

Ditto couldn't have put it neater myself........................ er wait a minute whats an ILS????? I don't use those anymore :p lol.

Si

No, this is not an AW139 "thing". More likely poor instruction or a misunderstanding.
From the AW139 QRH:
"...APP mode should be armed when the helicopter is flying inbound to the ILS radial"
"APP" will arm the localiser and glideslope.

He did mention (as far as he was aware) the instructor had no time on the actual machine (139)....

Hi 2F1B

Whilst coupling modes will usually cope with a 90deg intercept, you shouldn't arm the approach modes until you are cleared to intercept. Although it is unlikely, there is always the possibility that ATC will want to vector you through the centre line for separation and you will be a little embarrased if the autopilot takes you off towards the runway.

Cheers

TeeS

HC, don't need Geoff.
Whoever teaches to arm the automation in the 139 right before intercepting the GS is not letting you play with a full deck of cards.
The automation in the 139 allows you to switch seamlessly from FMS to short range NAV modes and it also allows the pilot to shoot an ILS or VOR approach the old way, by arming the APP when on radar vectors to final.
The crew needs to be aware of the correct Navigation Source selection for the respective mode of navigation, the risk being to fly through the FAC without the automation capturing it.

The only limitation, other than speed for a glide slope of 7.5*, is MAXIMUM RECOMMENDED Localizer intercept angle of 45* @ ranges above 10nm or 30* when inside 10nm.

Mark Six, you are quoting the QRH out of context, what you wrote is a NOTE not a limitation, and it actually states:

Note
To avoid false localizer captures, APP mode should be
armed when the helicopter is flying inbound to the ILS radial. (I know, localizers haven't got radials BTW)

Remember that you need to get established onto the LOC before capturing the GS.

Where, I wonder...?

Tottigol, I never said or implied that the quote I inserted was a limitation. It is contained in the Normal Procedures section of the QRH, and regardless of the context it is still relevant to this discussion as it appears to contradict what the original poster was told. I can't find any other relevant reference from the manufacturer.

Tott,

What happens if you forget your Approach Gun and cannot "shoot" the ILS Approach? Revert to a Localizer Approach?:=

It, like most things, depends
 

Easy answers are usually too simplistic.

To allow your Autopilot (or yourself) to change your heading to start flying the final approach course or to change your altitude to begin following the glide slope you must have received an approach clearance; period. Simple straight forward.

May you arm the system prior to that? Surely, but understand your system and how you're approaching the course and g/s. If doing a procedure turn, if you arm too early and accidentally intercept the course while still nearer the heading of reciprocal of the inbound than the inbound, many APs will turn and track the localizer outbound. In the H60M, the system (they call it a Flight Director not an AP) gives priority to the inbound course by 105° to 75° for which direction to turn. You had better know where the glideslope is relative to the aircraft also. The norm is g/s above you.

My general guidance to the pilots I trained was to arm the FD/AP when they met all of the following conditions:
1. avionics is properly configured, tuned, identified
2. cleared for the approach
3. system had switched from BC (back course) to LOC
4. below or on the g/s
5. you're ready

I was taught to arm it with 45 degrees of the approach course and below g/s


Soave

OK,what is the subject of this thread, "when should we arm the APP mode in general" or "when to do it in the 139"?

If you are flying a WWII aircraft, like a '412 or a '76 and all you have is VOR/ILS/DME then, by all means push that APP or ILS button on your FD controller only when ATC has given you the final vector to "intercept the LOC" and cleared you for the approach, and you are in a position to do so.

For the rest of you in the 139, when using the PRV mode or on HDG mode because receiving vectors to the FAC, arming the APP mode works the same way allowing the system to capture the LOC first and the GS if correctly positioned and the APPROPRIATE MODES are ENGAGED and CAPTURED in the FD, so caution ought to be excercised to have been cleared for the approach before pushing that button.

BB, even you folks south of LA82 ought to know the meaning of shooting an approach, so your remark is not clear.

Mark Six, that note may be in the blue side of the QRH, it is however a note to remind the crew that arming APP when flying in the wrong direction :E (as in away from the localizer) may result in "startling" manouvering. You are right, you never implied it was a limitation because the only limitation for that purpose is the one I specified with regard to the intercept angle and distance from the localizer, so if you are whithin those angles you don't need to be "almost right on top of the GS".

One more word of caution applies to reporting information heard from someone who heard it from someone else, you know the drill.

I agree with SND, Bravo 73 and HC, in actual operations, that's how its done.