Landing before displaced thresholds?
- Thread starter kestrel
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mvivion
FOUNDER
Bozeman,MT
From the Aeronautical Information Manual, under Aeronautical Lighting and Other Airport Visual Aids:
"Displaced Threshold. A displaced threshold is a threshold located at a point on the runway other than the designated beginning of the runway. Displacement of a threshold reduces the length of runway available for landings. The portion of runway behind a displaced threshold is available for takeoffs in either direction and landings from the opposite direction. A ten feet wide white threshold bar is located across the width of the runway at the displaced threshold. White arrows are located along the centerline in the area between the beginning of the runway and displaced threshold. White arrow heads are located across the width of the runway just prior to the threshold bar, as shown in FIG 2-3-4."
MTV
"Displaced Threshold. A displaced threshold is a threshold located at a point on the runway other than the designated beginning of the runway. Displacement of a threshold reduces the length of runway available for landings. The portion of runway behind a displaced threshold is available for takeoffs in either direction and landings from the opposite direction. A ten feet wide white threshold bar is located across the width of the runway at the displaced threshold. White arrows are located along the centerline in the area between the beginning of the runway and displaced threshold. White arrow heads are located across the width of the runway just prior to the threshold bar, as shown in FIG 2-3-4."
MTV
kestrel
PATRON
Southern NH
Last I knew, (though it seems to be sliding) the AIM was not regulatory. Also, I can land on the grass in a location that is not a runway at all. So, I don't disagree with any of your reply, but it isn't clear to me that landing before a displaced threshold is disallowed by the FAA.
FAR 91.129.e.3 (Class D operations)
Each pilot operating an airplane approaching to land on a runway served by a visual approach slope indicator must maintain an altitude at or above the glide path until a lower altitude is necessary for a safe landing.
Maybe we can argue that it is safer to keep the bushwheels off the pavement.
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Sourdough75
FRIEND
Tulsa, OK & Aleknagik, AK
I did see a guy in a Mennonite hat that used to land in the grass, power up to turn left on the numbers and taxi off on 24 at Merrill. It was pretty sporty, even though he was a Georgia Tech graduate. The world needs more people like Ed.
Waldo M
MEMBER
Finger Lakes area, western NY.
They don't. They do know the F.A.R.s though. Keep it up if you would like to experience a 709 ride with an FAA safety inspector.
bob turner
Registered User
Fascinating! I was just going to start a thread about a similar situation.
I need to explain how to establish an approach so that the aircraft stays on a constant angle of descent until flare. I demonstrate them, and mumble stuff about how much easier it is to see the runway if you either come in at idle or approach behind the power curve.
I also mumble a bit about stick controlling airspeed and power for altitude.
But what I need is a good discussion as to why "dragging it in" is not the best idea.
We did two of those today - the first I just said "getting kinda low there, partner." The second time we touched down 6" short. That is ok, sort of, on a runway with a displaced threshold, but not a great idea otherwise.
But no - do not land before the threshold. Recently, any operation outside the confines of the runway during takeoff/landing will get you a discussion with the FSDO.
Our tower is currently pretty quiet when we "miss" - but still . . .
I need to explain how to establish an approach so that the aircraft stays on a constant angle of descent until flare. I demonstrate them, and mumble stuff about how much easier it is to see the runway if you either come in at idle or approach behind the power curve.
I also mumble a bit about stick controlling airspeed and power for altitude.
But what I need is a good discussion as to why "dragging it in" is not the best idea.
We did two of those today - the first I just said "getting kinda low there, partner." The second time we touched down 6" short. That is ok, sort of, on a runway with a displaced threshold, but not a great idea otherwise.
But no - do not land before the threshold. Recently, any operation outside the confines of the runway during takeoff/landing will get you a discussion with the FSDO.
Our tower is currently pretty quiet when we "miss" - but still . . .
Richgj3
BENEFACTOR
LI,NY
A while back a guy at our airport put a Fleet 16B on its back by dropping in in. In addition he did this short of the displaced threshold. Since the Feds had to show up they saw where the Fleet hit the ground. The only thing that caused him the 709 ride was that he landed before the threshold. They didn’t care about the rest of it.
Rich
Rich
Farmboy
SPONSOR
Fort Edward, NY - Fairview, OK
I need to remember this one so I can request a departure in the opposite direction from the displaced threshold. Hahaha. Sounds like fun.
“Yes tower, the AIM specifically states I can”.
Transmitted from my FlightPhone on fingers… [emoji849]
Farmboy
SPONSOR
Fort Edward, NY - Fairview, OK
So, here’s a little response from an inspector…
“Only the FAR’s (front portion of the FAR/AIM) is regulatory”
“However it would be considered bad judgement to ignore a displaced threshold…
….Especially if that displaced threshold is at a towered airport”
That said, as an advisory it’s not a legal problem. Until the individual that perceives it as a problem simply violates you on a careless and negligent “unsafe” operation and throws that aforementioned ride at you.
Sent from my iPhone using SuperCub.Org
“Only the FAR’s (front portion of the FAR/AIM) is regulatory”
“However it would be considered bad judgement to ignore a displaced threshold…
….Especially if that displaced threshold is at a towered airport”
That said, as an advisory it’s not a legal problem. Until the individual that perceives it as a problem simply violates you on a careless and negligent “unsafe” operation and throws that aforementioned ride at you.
Sent from my iPhone using SuperCub.Org
kestrel
PATRON
Southern NH
I haven't seen that in FAA writing yet, but that is my belief. I don't normally fly a 3 degree glide slope. The astounding thing is: "The portion of runway behind a displaced threshold is available for takeoffs in either direction"
...you can count the far/departure end displaced distance as part of your takeoff? I wonder if that is meant for an abort and not a "takeoff"?
kestrel
PATRON
Southern NH
As mentioned in a previous post, class D has some requirements to not fly below any visual glide slope indication.
The runway below is not in class D. No tower. No VASI. No PAPI. The threshold is displaced 1,095 ft. About 200 ft beyond that is a crossing runway. I've heard someone state on the radio that it isn't possible to land on 32 and hold short of the crossing runway because of the displaced threshold. This was several years ago and I wasn't sure who they were talking to.
...and yet it is routine (for some at the airport) to land on the grass on the south side of the runway and stop short of the taxiway.
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Farmboy
SPONSOR
Fort Edward, NY - Fairview, OK
Well, now that you mention it, seems I’ve been a repeat offender at that airport Kestrel.
“So that’s what those arrows are for eh”.
And perfectly acceptable to take a 14 departure from either Alpha intersection. Lol.
Sent from my iPhone using SuperCub.Org
“So that’s what those arrows are for eh”.
And perfectly acceptable to take a 14 departure from either Alpha intersection. Lol.
Sent from my iPhone using SuperCub.Org
skywagon8a
MEMBER
SE Mass MA6
Why does that runway have a displaced threshold for landing? You may find the answer here:
https://www.icao.int/NACC/Documents...ACertification2012/ICAOFAACertification15.pdf
It's likely due to obstruction clearance requirements in the approach zone. This does not mean you can not use the full length for take off unless the airport has a prohibition against it. Chances are the reason for that displacement was so that airport could lengthen the runway for take off without meeting the landing clearance requirements.
Grant
MEMBER
At Work.....
kestrel
PATRON
Southern NH
I expect that you are correct. However, those standards are for jets. Jets won't be landing on the side grass, which seems to be considered a reasonable thing for appropriate aircraft to do. Not all aircraft are limited to a 3 degree glide slope.
kestrel
PATRON
Southern NH
What percent of the activities enjoyed by the members of this forum fall outside of the AIM and standard airport requirements? What percent might fall under 91.13 if someone with authority decided that they didn't like you?
I get your point, but I don't think it sticks. I still don't see a regulation that makes it illegal to land before a displaced threshold just as I don't see one that prevents landing on the grass out side the lateral bounds of a runway. I have very limited AK experience, but I understand it is common to land bushwheels before thresholds. On some runways, with some aircraft it is very reasonable and not reckless to land before a threshold.
skywagon8a
MEMBER
SE Mass MA6
I don't know about New Hampshire airport requirements, but in Massachusetts the type of powerplant is not part of the approach obstacle clearance criteria. In fact, the criteria has been in place since prior to the invention of jets. At my airport (28M) we were having an issue with being allowed to cut trees. Mass Aeronautics suggested we paint a displaced threshold line on the runway to comply with the approach and side clearance requirements. This displaced threshold would not apply to take offs. We eventually won the right to clear the trees.
Why is there a displaced threshold at this airport?
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skywagon8a
MEMBER
SE Mass MA6
That is another reason. Some of the big airports do that on purpose to help slow an airplane if it overruns the runway. The wheels dig in helping the slowing.
sj
Staff member
Northwest Arkansas
Regulations aside, I have sent a LOT of Flip Flop hats out to folks who used the grass to save their bushwheels and ended up with a rebuild.
Also, the "start" of the threshold is not always a smooth transition from the grass, so "know thy threshold".
In my experience, it is lots of taxing and heavy braking turns on asphalt that wear out bushwheels - not landing so much. In the early 00's we did over 2000 landings on a set of 31" tires on pavement (including taxiing) before the wore out. Assuming manufacturing is the same today, that's a lot of landings. Of course, it's $2 per landing but do the landing math with your insurance for comparison.
sj
Also, the "start" of the threshold is not always a smooth transition from the grass, so "know thy threshold".
In my experience, it is lots of taxing and heavy braking turns on asphalt that wear out bushwheels - not landing so much. In the early 00's we did over 2000 landings on a set of 31" tires on pavement (including taxiing) before the wore out. Assuming manufacturing is the same today, that's a lot of landings. Of course, it's $2 per landing but do the landing math with your insurance for comparison.
sj
frequent_flyer
Registered User
Arizona, USA
I suspect the side scuffing when landing on gear with large changes in geometry (track and camber) is a significant factor. The gear didn't move at all when I 3 pointed my FX-3 on stock bungee gear. Now I have the Acme shocks I'm sure the tire wear will increase as the shocks always extend a bit even with zero sink rate landings.
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Asphalt taxi and sharp turn wear is easy to see. It looks like I took a grinder to my tires. Just turning onto an asphalt runup pad at a gravel strip grinds the tires. When I’ve touched down on pavement enough to spin up the tires and rolled out on gravel and dry grass I can’t see any evidence of the touchdown.
The camber in my 180 gear flexes with every takeoff and landing. If anything it distributes the wear surface on the tires but rotating tires (valve stem in-valve stem out) per ABW recommendations is always a good idea.
The camber in my 180 gear flexes with every takeoff and landing. If anything it distributes the wear surface on the tires but rotating tires (valve stem in-valve stem out) per ABW recommendations is always a good idea.
mvivion
FOUNDER
Bozeman,MT
First, the FAA recently "authorized" or perhaps a better term would be recognized, landings and takeoffs in the Runway Safety Area (RSA) alongside a runway, WITH airport management and or ATC authorization. Some airports and ATC facilities have permitted this in past. Here in Bozeman, request to land in the grass adjacent Runway 03, and Tower will say "landing in the grass next to runway 3 will be at pilots own risk". In past, that was just something some airports did, but many didn't do. Now, this is at least recognized by the FAA as a "thing", so hopefully more airports will allow it.
But, that new policy doesn't say anything about Displaced thresholds. I suspect 91.13 may be most often applied after an accident or incident, where the pilot deviated from "Normal procedures", but who knows. Nevertheless, my policy has always been to avoid opening any door which MAY put me in the crosshairs. Your mileage may vary.
So, if you're so sure it's not a thing, call up your local FSDO, and tell them to stand along side runway xx displaced threshold at whatever time, and you'll demonstrate a landing therein. 8)
Then report back here.
MTV
kestrel
PATRON
Southern NH
Between the thresholds is officially endorsed for normal landings at the stopping end (departure end? Non-approach end?) and at both ends for departure. It doesn't make sense to have a weak surface there. There would be hell to pay if a wheel dug in using a surface as endorsed.
BC12D-4-85
SPONSOR
Fairbanks, AK.
Got to be an obstacle clearance or ILS component tolerance issue.
Gary
Gary
kestrel
PATRON
Southern NH
I think I wasn't clear about my meaning. The standard is intended to create safety for all aircraft, including jets. Including jets in the standard is over kill for aircraft that can fly steep approaches.
Why is there a displaced threshold at this airport?I think you know the owner?
In years past it was at the far edge of the turn-around/run-up space on the right. Only a small displacement. The FAA required that it be moved much further because of the hill. It is entirely reasonable for some aircraft to touch down well short of the threshold without endangering anyone or any thing.
The north end used to have no displacement. The threshold lights were in the short section of grass before the hill. The FAA also required a displacement there because of the trees on the north end. It is note worthy that the number of aircraft that nearly wiped out their gear on the hill top by accidentally landing short of the pavement was larger than it should have been.
They are displaced as required by the FAA to aid those that don't know how to fly. I don't know why the original locations had been fine for decades and then had to be moved.
arborite
SPONSOR
Ann Arbor, MI
Interesting discussion. I flew in to Oshkosh early this year before the NOTAM took effect, so flew direct to airport. ATIS noted nonstandard runway markings. I assumed that meant the colorful dots on the runway and didn’t think anything of it. Was assigned a left downwind to runway 18. Turning onto a short final, i noticed a painted line across the runway ahead (marked in red in the image). I didn’t have time to really figure out what it was, but guessed it was the displaced threshold marking for 18 when the NOTAM took effect. Still not sure. Decided to power up a bit and land beyond that line to be on the safe side. I’ve never intentionally landed prior to a displaced threshold - no need to. I do land on the grass adjacent to the pavement at several uncontrolled fields in our area, as do many. Instructors use it for tailwheel students as well, so I don’t fret much about the legality. At our local towered field, if we land in the grass there, we often get the “at your own risk” comment as well. One of these days, i’ll work up the guff to reply “Aren’t they all?”.
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