Using GS,when not aligned with LOC (vis)

[your_dreamguy]

Hey Everyone,
I'm a pretty new FO. The other day I was FP going visually to an airport I'd never been into before. It was night and the this was a small airport with the lights real dim. Well, we were coming in on base (we never did a downwind entry, so I never saw the runway) and I had the hardest time picking up the runway and runway lights. Subconiously, I stayed high. As I got closer, I ended up high and fast. We landed the plane but we nearly had to do a go-around and the Capt. was pissed. On the ground, the capt said he had put in the ILS freq. in my radio (and he did do that) as backup. He told me that I could have used the GS indications on base leg to get a good feel for descent and proper altitude on base (even though, we were not aligned with the LOC) because we were going visually.
I've never heard of that technique before.
Any thoughts?

 

[mar]

Visuals at night: risky.

Some countries don't even allow visuals at night. Canada, I think, is one.

Since you were the flying pilot you probably briefed a standard visual approach.

Your captain tried to help you out with the LOC/GS but didn't bother to say anything about it until after the landing.

It's good technique to back up a visual with the LOC/GS but it sounds like poor CRM to let a new FO fumble through a pretty difficult manuever.

Yeah, a visual at night can be very difficult. You're VMC but need to manuever by instruments.

You need a strategy:

Plan to position the airplane 5 to 6 miles from the threshold at about 1500' above the field elevation. At that point you NEED to be configured and on-speed, on centerline.

That, by definition, is stablized. From there it should be a piece of cake.

But there are things to watch out for:

--showers in the area
--hills/peaks in the area
--VFR traffic in the area

Obviously a full moon helps especially with fresh snow on the ground.

No moon or overcast conditions at a remote airport and you could be asking for trouble.

I much prefer the full approach when manuevering at night.

I get paid by the hour.

I hope this helps.
Fly safe.

 

[Wankel7]

Yeah, I use that method almost anytime I am doing a visual in something other than severe clear. Also, if there is a back course I set up the to use the loc. If it is dark and I am having trouble finding the runway. It does help you sometimes.

Wankel

 

[saabcaptain]

the GS of course can be inaccurate when off the LOC but in many circumstances it isn't that "off." i often use it as a guide to confirm my visual perception of the runway and our HAT is in the ballpark before i turn on the LOC. i would not use it as a guide to decend visually if i didn't also see the runway (of course not being the LOC in my situation.)

 

[avbug]

If not on the localizer, disregard those glide slope indications. Not as a reference, not as a guide, not as anything. Until you are on the localizer, the glideslope does not exist. Forget what the captain told you; he's out of line and incorrect. When you're lined up with the runway you can use that guidance, or if you're flying an LDA with electronic glideslope (that's not aligned with the runway) you can use the vertical guidance...so long as you're established on the localizer.

But not otherwise.

Severe clear or hard IMC...don't use the glideslope unless you're on the localizer. This is doubly true at night.

 

[Ty Webb]

First of all, if you are flying a turbojet aircraft, and there is a precision approach for that runway, you are required to have it tuned in. If there is a G/S, you are required to use it. Presumably, with the localizer tuned, when you roll final, you should be aligned with the localizer . . . otherwise, you may not be where you think you are!

If you are not aligned with the localizer, such as on base, you can still add the G/S to your scan, just don't blindly follow it. It is one more piece of information. A good idea is to use the "3 to 1" ratio. . . . if you are turning a 5 mile final, plan to be at 1500' when you roll out on final, a 4 mile final, be at 1200 AGL. If your G/S is pegged when you are on base, it's a big hint that you probably need to evaluate descending.

 

[Turbo]

Make sure you have the airport or the preceding aircraft in sight before you ever accept visual approach.

 

[de727ups]

In spite of Avbugs comments

I use the G/S all the time as a sort of VNAV, even though not on the localizer centerline. For example, I fly the Jawbn9 arrival into BFI all the time. Jawbn intersection is not on the centerline of the LOC, and yet I get a quite accurate indication of a three to one of my vertical position by looking at the Glide Slope needle. Do the math based on a three to one to back up the G/S indication. I've found them to be quite accurate but I don't take it as gospel unless I've flown the procedure before and it has worked for me in the past.

They have some pretty amazing LOC/GS transmitters in Warsaw, Poland. I've been 100 miles from the station and got a good ident and good G/S indications based on a three to one. No reason not to believe the G/S.

your dreamguy....in response to your specific situation. I agree with your Capt tuning in the LOC for G/S indication. Ty Webb is right, too, you should be thinking about the need to be on G/S, if available. As your Capt, though, rather than be pissed with you after the fact, I would have said "you're looking high and why not take a look at the G/S needle to prove it", while on the visual. A good Capt won't compromise safety to prove a point.

 

[91100 100 set]

I don't know the technical stuff for sure, but I've seen the GS needle do some pretty strange things if you're not close to the LOC. Doesn't the AIM say something about 30 degrees off the LOC?

Your best bet is to figure about 300 feet per mile (a 3 degree slope is about that), and maybe some extra to slow down if you need it. And thats not always straight to the airport if you're entering into a downwind or something. Figure that distance for your planned track over the ground. It works out just fine.

 

[enigma]

Tuning the ILS in for a back up is proper standard practice and is regulatory for many operators. However, the FAA expects that a pilot will know and follow the AIM guidance for proper usage. Here's what that means, follow Avbugs advice. Never, ever, rely on a GS unless you are within its published service volume. I don't have the AIM memorized, but I believe that you have to be within 35degrees of the localizer and within 14 miles of the threshold. Otherwise, you could find a mountain between you and the runway.

regards,
enigma

 

[enigma]

the GS of course can be inaccurate when off the LOC but in many circumstances it isn't that "off."

Spoken like a flatlander. I'll never forget my first night visual into Kingman AZ. We came from Phoenix and it was my first night (nontraining) approach/landing in scheduled service. Being a flatlander myself, I called visual as soon as we descended below 180 and made a beeline for the airport lights. The Captain let me continue for a few miles, trying to give me the benefit of the doubt, before he tore me new one. I understand that this particular story is a little off from the exact subject of this string, but it is pertainent. You see, soon after he explained to me that there were rocks in the "clear" visibility between me and the airport, he impressed upon me the need to always utilize a published altitude and track when on night visual arrivals. He also impressed upon me the that it was foolhardy to ever descend off of a published altitude until I was on a known track. The short lesson is this, until you are on the localizer, you DO NOT KNOW exactly where you are.

Ignore the GS until you can verify that you are on the proper one.

regards,
enigma

 

[Hovernut]

Another good technique is to set the altitude alerter to the GS intercept altitude at the OM, then, if you have VNAV enabled, the 'bananna' shoud show you if your current rate of descent will get you to a good altitude to begin your final approach. Don't cut yourself short on the base; fly it to the OM and if you reach the target altitude, you'll be in like 'Flint!' (dating myself with that James Colbern flick!)

Also, if you're so equipped, by all means utilize the terrain mapping function of the PFD. That'll help identify any unseen hazards in the area.

And finally, you as the FP get to make the FINAL decision as to what kind of approach you want. If you're uncomfortable making a viz to an unfamiliar airport with the turn to the CA's side, by all means request and execute the published instrument approach for that runway. You're not only being safe, but as a previous poster said, we're paid by the minute. So, an extra couple minutes getting vectored and having ATC help you out is not only safe, but profitable as well.

Don't ever let an anxious CA or ATC pressure you into a situation you're not comfortable with.

 

[A Squared]

There's a couple of questions being answered here and the answeres are being mixed a bit.


Question one, does the GS give you useful and or accurate descent information when you are not on the localizer course.

Yes it does, but the further from the LOCalizer course you are, the less accurate it is. Still, if you follow the GS, it may bring you in a little steeply, or a little flatter, but it's going to e in the ball park and as you converge on the loc course, it will meet the correct 3 degree glidepath.


Question 2, can you rely on the GS for terrain clearence when you are not on the LOC course.

The answer to that is absolutely not. If you are on a night visual, your plan for keeping out of the rocks had better be based on something other that staying on the GS.

I have to take exception to a statement that Enigma made, to wit:

"Never, ever, rely on a GS unless you are within its published service volume. I don't have the AIM memorized, but I believe that you have to be within 35degrees of the localizer and within 14 miles of the threshold. Otherwise, you could find a mountain between you and the runway."

You are correct that the service volume of the *LOCALIZER* is 35 degrees either side of LOC centerline, out to 10 NM. However the statement might leave one with the impression that terrain clearence would be provided within that 70 degree arc. This is absolutely incorrrect. Here's the real story about terrain clearence on the GS. If you are more than 9 degrees off the LOC, you are in a zone of diminishing terrain clearence. If you are more than 14.5 degrees off the LOC you are outside the obstruction clearence area and have absolutely no terrain clearence protection. You may in fact fly right into a mountain if you are 15 degrees off the LOC and on the GS.

Can you use the GS as a descent planning aid in visual conditions when terrain is not a consideration? Yes

Can you depend on the GS for terrain clearence when not on the LOC or when outside of the outer marker? No

 

[Snoopy58]

oh, brother.

"The GS doesn't exist until you're centered on the LOC." Nonsense.

While you certainly don't descend on the GS until you're established on the LOC when in IMC or even when flying an ILS procedure in VMC, AND you certainly need to be aware of the limitations of the GS when you're far from the LOC centerline, AND you need to maintain SA regarding terrain & general distance from the threashold...

... nevertheless, when you're on base, thinking to yourself "okay, I COULD start a descent now, if I need to, but DO I need to?" the GS indicator can give you an EXCELLENT tool to use to help yourself. If you see it pegged at the top of the case, that's a good sign that you probably don't need to start down yet. If you're on base, about to turn final, and you see the GS centering up & heading toward a "high on GS" indication, that's a good clue that a descending final turn might be indicated.

NONE of this is a substitute for good SA, and you can't blindly rely on any, ANY, single piece of information without confirming it with all the other things you have available (VASI's, if you have them, DME, if available, VNAV info in the FMC, familiar landmarks, "does this look right" looking out the window, "hey Captain, this look about right to you?" etc etc etc).

But to say that you SHOULDN'T include the GS as one of the available tools that you consider as you contemplate descending in VMC as you approach final, is just plain bad advice.

 

[apdsm]

Another 2-cents

First off, I'm sorry you had to fly with jerk...
I bet he's NEVER done anything like that, nor will he do it again!
So you almost had to do a go around. Big deal.

As far as following the GS, I would say don't blindly follow it. Use it as a back up for your visual approach. If you are not comfortable decending and you are getting high, then start configuring and slowing rather than decending. In this case, you are just using the GS to confirm that yes, you are high, but you are not doing anything unsafe!

 

[JJJ]

What kind of airplane are you flying and does it have FMS or any fancy stuff like that?

 

[Immelman]

Am I the only one that is wondering what the heck you're doing on a visual approach w/o runway in sight? Was this not IFR?... Seems to me you need things in sight to be cleared for a visual...

And if it wasn't IFR, why not?

Please realize I am a junior pilot compared to just about all of you and prefer the seat of pants flying to IFR, etc... but the story just smelled fishy to me.

 

[Caveman]

A Squared posted:

"Can you use the GS as a descent planning aid in visual conditions when terrain is not a consideration? Yes

Can you depend on the GS for terrain clearence when not on the LOC or when outside of the outer marker? No"


I agree. Use the GS as a guide to help you manage your descent recognizing the following limitations:

1. It won't be perfect unless you are on the localizer.
2. The farther you are from centerline the less accurate it will be.
3. Don't rely on the GS for terrain clearance unless you are within a dot or two of centerline.

 

[enigma]

I have to take exception to a statement that Enigma made, to wit:

"Never, ever, rely on a GS unless you are within its published service volume. I don't have the AIM memorized, but I believe that you have to be within 35degrees of the localizer and within 14 miles of the threshold. Otherwise, you could find a mountain between you and the runway."

You are correct that the service volume of the *LOCALIZER* is 35 degrees either side of LOC centerline, out to 10 NM. However the statement might leave one with the impression that terrain clearence would be provided within that 70 degree arc. This is absolutely incorrrect. Here's the real story about terrain clearence on the GS. If you are more than 9 degrees off the LOC, you are in a zone of diminishing terrain clearence. If you are more than 14.5 degrees off the LOC you are outside the obstruction clearence area and have absolutely no terrain clearence protection. You may in fact fly right into a mountain if you are 15 degrees off the LOC and on the GS.

Thanks for the backup. I was so focused on getting the point across that you can't just follow the gs, that I didn't realize that I was leaving the impression that you could rely on it within its service volume. So, if I confused anyone, re-read AA's post. Maybe I should have said this, do not rely on the gs unless your position can be positively verified and you are established on the final approach segment. Don't even go there about the meaning of established, it isn't defined. I consider established to mean on centerline.

Thanks again AA,
enigma

 

[Rez O. Lewshun]

Never do a night approach with out electronic or visual vertical guidance.