Dipping under the GS

[kngarthur]

Is there any time when it is permissable to dip under the glide slope during the landing flare? Thanks!

 

[AA717driver]

Is there any time when it is permissable to dip under the glide slope during the landing flare? Thanks!

When you are visual, you are permitted to go below the GS as long as a safe landing is ensured. Just inform the guy you're flying with so he doesn't get nervous.

I've always done it on shorter runways or when it's busy so I can make an earlier turnoff. TC

 

[XJTAv8r]

Is there any time when it is permissable to dip under the glide slope during the landing flare? Thanks!

@ MDW...lol. Has anyone else noticed the many tire marks before the displaced threshold on 31C?

Off the top of my head, you can transition to the VASI/PAPI when it's in sight. That might get you a little lower. I think you can find an official answer in the AIM.

 

[Beanie]

Ok, it is official. I am getting old. Questions like this now illicit the response out of me that I would see in my father and grandpappy. Are you stupid are just plain dumb? RTFM! Here is an idea. Instead of taking someone's word for it, who could be wrong be the way, why don't you get off your a$$ and do some research? Start with reading the FAR/AIM maybe....Not only is it a credible source, you might run across a few other things that you didn't know and increase your knowledge base. Imagine that, you could actually accomplish something that your spikey haired, backpack wearing dude friends have yet to undertake, professional continuing education! Taking shortcuts is no way to go through life kid.

Now, I have to go take my geritol, some back pills and try to get my morning BM out of the way before noon.

 

[mooney flier]

See FAR 91.129(e)(2),(3).

 

[EMB170Pilot]

Ok, it is official. I am getting old. Questions like this now illicit the response out of me that I would see in my father and grandpappy. Are you stupid are just plain dumb? RTFM! Here is an idea. Instead of taking someone's word for it, who could be wrong be the way, why don't you get off your a$$ and do some research? Start with reading the FAR/AIM maybe....Not only is it a credible source, you might run across a few other things that you didn't know and increase your knowledge base. Imagine that, you could actually accomplish something that your spikey haired, backpack wearing dude friends have yet to undertake, professional continuing education! Taking shortcuts is no way to go through life kid.

Now, I have to go take my geritol, some back pills and try to get my morning BM out of the way before noon.

You pretty much summed kngarthur up.

 

[kngarthur]

Ok, it is official. I am getting old. Questions like this now illicit the response out of me that I would see in my father and grandpappy. Are you stupid are just plain dumb? RTFM! Here is an idea. Instead of taking someone's word for it, who could be wrong be the way, why don't you get off your a$$ and do some research? Start with reading the FAR/AIM maybe....Not only is it a credible source, you might run across a few other things that you didn't know and increase your knowledge base. Imagine that, you could actually accomplish something that your spikey haired, backpack wearing dude friends have yet to undertake, professional continuing education! Taking shortcuts is no way to go through life kid.

Now, I have to go take my geritol, some back pills and try to get my morning BM out of the way before noon.

Why this is just easier? It's not like this stuff is brain surgery? Maybe for you though!

 

[FlyBoeingJets]

Is there any time when it is permissable to dip under the glide slope during the landing flare? Thanks!

Yes, after you are on the visual portion of the approach at an altitude lower than decision height. I wouldn't say I was dipping below. Just transitioning to visual references.

AND

The Check Airman you are flying with doesn't have a "Thing" about staying on the glideslope.

 

[FlyBoeingJets]

See FAR 91.129(e)(2),(3).

http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?&c=ecfr&sid=3efaad1b0a259d4e48f1150a34d1aa77&rgn=div5&view=text&node=14:2.0.1.3.10&idno=14#14:2.0.1.3.10.2.4.16


(e) Minimum Altitudes. When operating to an airport in Class D airspace, each pilot of—

(1) A large or turbine-powered airplane shall, unless otherwise required by the applicable distance from cloud criteria, enter the traffic pattern at an altitude of at least 1,500 feet above the elevation of the airport and maintain at least 1,500 feet until further descent is required for a safe landing;

(2) A large or turbine-powered airplane approaching to land on a runway served by an instrument landing system (ILS), if the airplane is ILS equipped, shall fly that airplane at an altitude at or above the glide slope between the outer marker (or point of interception of glide slope, if compliance with the applicable distance from cloud criteria requires interception closer in) and the middle marker; and

(3) An airplane approaching to land on a runway served by a visual approach slope indicator shall maintain an altitude at or above the glide slope until a lower altitude is necessary for a safe landing.

 

[satpak77]

Is there any time when it is permissable to dip under the glide slope during the landing flare? Thanks!

when you can safely land visually (day, night, marginal VFR, etc etc)

period, end of story

dont make this hard...

 

[Jim Smyth]

Unless you practice this on a regular basis on clear VFR weather days (preferably on very long runways with no threshond issues) you will most likely overshoot the touchdown zone while dipping below when you get into ground effect. Its better to do the same landing every time and touchdown between the 1000 and 1500 foot point, on glide path and you dont have to worry about hitting anything. If you dont believe me look at where the most rubber on the runway is located.

 

[SWA/FO]

never

 

[Bubba Dog]

Would not recommend it in low vis or low light conditions. Try to shoot for no more than one dot below if you do decide to get off the glideslope. There have been a lot of folks either killed or drug their gear through the approach lights trying to dunk under. A glide slope is a invaluable aid,use it whenever you can.

 

[Whine Lover]

"Taking shortcuts is no way to go through life kid."


Yes...It IS.


YKW

 

[labbats]

Common sense is half of flying. If there's no windshear and you're in visual daylight conditions with no worries of plowing under the approach lights, why not give yourself some more runway to roll out on? Or for passenger comfort why not land it on the 1000' bars and then let it roll instead of being a brake smasher and plowing some bluehair into the seat in front of them to make the first turnoff.

Of course the same could be said for beginning and finishing your climb/descent rate, but that's another story.

 

[Big Beer Belly]

Common sense is half of flying. If there's no windshear and you're in visual daylight conditions with no worries of plowing under the approach lights, why not give yourself some more runway to roll out on? Or for passenger comfort why not land it on the 1000' bars and then let it roll instead of being a brake smasher and plowing some bluehair into the seat in front of them to make the first turnoff.

labbats ... not meant to be derogatory to you ... but noticed you did not list any large aircraft in your resume. Anyone with large aircraft experience unconsciously cringes with your suggestion. I understand this "might" be acceptable in certain situations in small aircraft, but it is a very unwise move in big jets.

Here's an example I'm familiar with. Let's take a B767-300. If the aircraft is on glideslope and the radar altimeter indicates we cross the threshold at the recommended 50' our main gear tires are only 22' above the concrete across the threshold. There is not a lot of "ducking under" one can do without putting the aircraft in danger. In fact, threshold crossing height (i.e., no ducking under) is so critical that on an autoland below 300' AGL there is ZERO deviation BELOW glideslope allowed. Any deviation below GS requires an immediate go-around.

Moral of the story for LARGE aircraft ... fly the glideslope!

BBB

 

[Lear70]

I do it every single time going into MDW.

In 3 different transport category jets now plus the Lear (although I don't exactly place that in the same category).

I never go more than one dot below: stay on the g/s until you reach minimums, transition to outside reference (VASI / PAPI if available), increase your descent rate slightly, round-out, and land.

It doesn't increase your "float", have no clue what you're talking about; I've always put it on in the first thousand feet doing this. Increase float only happens if you let the airspeed creep up as you increase your descent rate; control your airspeed like you should and it's not a factor.

Incidentally, in both the CRJ and the 717 if you'll notice, staying on the glideslope has you crossing the runway threshold at 100 feet instead of the recommended 50.

If you'll go one dot below the g/s INSIDE the MM in these aircraft, you'll cross the numbers just as 'Betty' says "FIFTY". Incidentally, you'll also be right on the VASI / PAPI as well.

Perfectly legal, perfectly acceptable in VMC conditions under the "transitioning to land" provision in the FAR's and the AIM.

IMC or low-vis, I agree, just stay on the G/S and, in MDW, don't flare... Just slow the descent slightly and let her thunk on nice and solid.

And, incidentally Arthur, they're right. Go dig up the answer in the AIM; would suck if you bust an oral some day because you don't know the answer to a basic airmanship question (and it's fair game during any 121 oral).

 

[m80drvr]

Funny, I would think a plane like the 767 would adjust your RA for the altitude of the gear not the altitude of the antenna, like most of the rest of the transport AC do.

Belly, are you telling us that on the ground your RA says something other that 0? And if I did the math correct your gear is about 28 feet high. Wow the 76 is alot bigger than I thought

The bus auto calls are RA based and adjusted for wheels on the pavement not fuselage off the pavement. That 5 foot call would be worriesome if it were based on the antenna height.

I thought it was the same for the 80 but its been a long time since I've been in that plane.

Who said boeing is better.

 

[radarlove]

There is no such thing as "glide slope" once you're below decision height. The gauges are meaningless. So, yes, one can transition below glideslope on a 200' ILS if one is below 200', because again, there is no such thing as glideslope below DH.

 

[slaquer5]

There is no such thing as "glide slope" once you're below decision height. The gauges are meaningless. So, yes, one can transition below glideslope on a 200' ILS if one is below 200', because again, there is no such thing as glideslope below DH.

Thank you. I was going to say the same.

 

[m80drvr]

There is no such thing as "glide slope" once you're below decision height. The gauges are meaningless. So, yes, one can transition below glideslope on a 200' ILS if one is below 200', because again, there is no such thing as glideslope below DH.

Thats not quite true on a CAT II or III rwy but thats being picky. Sorry

 

[slaquer5]

Thats not quite true on a CAT II or III rwy but thats being picky. Sorry

I think RL said it right. if you are doing a cat 2 or 3 it is not called an ILS. it is called ILS Rwy XX CAT II & III... Even then it is still a visual at 100' or 50'

 

[Lear70]

Thats not quite true on a CAT II or III rwy but thats being picky. Sorry

I was going to say the same thing... LOL

I wouldn't completely disregard the G/S guys, it's accurate all the way to the runway in most aircraft, even if you're not Cat II or III (a, b, or c)-qualified.

 

[Peanut gallery]

Actually there is....

specific guidance 121- wise that allows a narrowbody aircraft to intentionally go below the glidepath 300 feet and below visually of course....

 

[m80drvr]

I think RL said it right. if you are doing a cat 2 or 3 it is not called an ILS. it is called ILS Rwy XX CAT II & III... Even then it is still a visual at 100' or 50'

A CAT II / III ILS uses the same antenna array as a normal ILS to that runway. The difference is the minimums and the protection of the ILS critical area. (and of course the certification of the approach but that is even more off topic) An ILS is still an ILS even if it has CAT II/III after it.


PS I'd love DC-3 rating.

 

[Big Beer Belly]

Funny, I would think a plane like the 767 would adjust your RA for the altitude of the gear not the altitude of the antenna, like most of the rest of the transport AC do.

Belly, are you telling us that on the ground your RA says something other that 0? And if I did the math correct your gear is about 28 feet high. Wow the 76 is alot bigger than I thought

On the ground, the RA will read a negative value (can't remember ... -4'/-6' ... would have to look it up ... 757 has similar though less dramatic main gear crossing concerns. 757 basically is opposite the 767-300. On GS the tires cross at 28'. Obviously these numbers vary with glidepath angle and airplane body attitude. Remember, the struts are not compressed and the trucks are tilted which, in effect, increases their length.

I'm no rocket scientist, but I'm sure Boeing employees a number of them and trust there's very sound engineering principles for why they design their aircraft the way they do. My guess is the entire line of Boeing aircraft follow a similar design philosophy for radar altimeter antenna placement and threshold crossing height concerns.

BBB

 

[m80drvr]

Belly

I understand what you mean. I would agree that the wheels would be lower that 50' on the GS since the antenna is not adjusted for gear height. Depending on deck angle and GS antenna placement I can see the 28' gear height. But I still have to wonder wonder what the RA displays if you are at 50' ON GS in the 76. I'd check the bus, but usually by 50' I have my eyes closed.

 

[Big Beer Belly]

I think RL said it right. if you are doing a cat 2 or 3 it is not called an ILS. it is called ILS Rwy XX CAT II & III... Even then it is still a visual at 100' or 50'

Not sure I follow you here. A visual at 100' or 50'? Are you suggesting the landing is a "visual maneuver" at those altitudes? If so, then in a broad sense you are mistaken. Perhaps your company (SWA?) is more restrictive or your aircraft less capable which may well dictate you see something prior to touchdown, but that is not an approach requirement across the industry or dictated by FAR's.

At UPS, there is NO REQUIREMENT to see anything prior to touchdown on 3b approaches and some 3a approaches (depending on autoland status) in the 757/767. Moreover, since an autoland is mandatory for all Cat 2/3's on the 757/767, and the autopilot could care less about ceiling and visibility, clearly it's not a "visual maneuver" (at least not at brown). As I said before, it may very well be a visual maneuver at your company due to your ops specs (equipment/training.)

BBB

 

[scoreboard]

I do it every single time going into MDW.
I never go more than one dot below: stay on the g/s until you reach minimums, transition to outside reference (VASI / PAPI if available),

For the young guys the key to his statement is stay on GS until DH. If fly one Dot low prior to DH, you place yourself at DH farther from the threshold than if you were on GS. This can be a problem if visability is at minimums. If you get to DH one dot low and visibility is at minimums, you will more than likely not be in a position to continue the approach IAW FAR runway environment requirements at DH and at 100ft.

I submit, that FAR's allow you to take-over visually and practically disregard GS on a CAT I. Cat II/III is a whole nother animal.

Fly safe!! Like, you would go out and fly dangerous...

 

[oldxfr8dog]

Don't

Just stay on the GS. Pitching it over at minimums (increasing descent rate), accelerating or reducing power to stay on speed, and de-stabilizing your approach gets you what, 200-400 foot more runway? If it's that tight, maybe you shouldn't be there.
This reminds me of a Capt I flew with years ago. He would add an addition 10 knots above the calculated "ref+ speed" and then he would announce, "Ducking under the GS" on final.
Another great idea is leaving such a comment on the voice recorder.