How does a 757 complete a 5.6 degree glide from 3,100' - Air Greenland BGBW
 

In the late 90's I used to go into London City (similar approach angle) in a 30 seat turboprop and we had to abort if flight idle was 2% above minimum value as we would accelerate and be unstable by 500'

So how did Air Greenland do this when they used to fly their 757-200 into BGBW a few years ago.

I can't find a Short Field Performance version as Boeing offer for the 737....or was it just an offset visual only approach?

Thanks in advance.

The only time that a steep approach is necessary at BGBW is when there is a strong wind up the valley. In that situation the effective approach angle into wind is considerably less than it would be with zero wind.

Many years ago I recall watching an SAS DC8-63 approaching down the glacier at BGBW, landing on the runway which also slopes down towards the fjord!

An exciting landing, needless to say, but they did get it stopped.

The only IMC approach is the 5.6 degree approach. As the Air Greenland operation was a regular service they must have either had to approach at 5.6 degrees....or had an alternative procedure for the NDB?

Perhaps by getting visual out over the ocean and flying up the fiord. I did that one in a small plane.

Our company used to fly 727's in there. Wx minimums were a little higher than normal.

Not many jet ops videos at BGBW but this one is interesting.


https://www.youtube.com/watch?v=JW3u_LkHnw0

The difference is in the requirements between precision and non-precision steep approaches.
At LCY the aircraft has to be capable of a continuous precision guidance steep approach to the flare and landing.

NPAs such as at BGBW may require a steep approach into a valley which allows a transition to a more normal flare and landing. Note the approach limits, 1500 or 2400ft MDA, and a day only restriction.

Absolutely right, PEI. In which case, the answer to the original question "How does a 757 complete a 5.6 degree glide from 3,100' - Air Greenland BGBW" should be "landing flap setting and Flight Idle power to the transition point should do the trick"

twochai, thanks. :ok:
I don't have a chart to hand, but a pedantic point is that 'glide path, (slope) is normally associated with a continuous descent to landing, whereas a 'required descent angle' implies a change in the vertical approach path.
The latter involves an unstable approach. Modern approach systems and procedures are designed to minimise such changes, but then require an aircraft which is capable of both descending steeply and flaring from the approach - probably excluding a 757.

Yes, PEI, but you know well that flying in the Arctic/Antarctic, the jungles and on water still requires SA and good judgement on the part of the pilot - be it a 757, C-17 or something smaller.

Long may it last!

The 757 manages the 5.31 degree approach at Katmandu OK,flap 20 and full speed brake. With the much lower density altitude I would expect it to cope with 5.6.

The airline that I flew 757's for ten years ago was in the habit of using BGBW as a non-ETOPS alternate from time to time. I was in the habit of refusing these flight plans. As I had a minor management position, I took the liberty of writing to the chief pilot at Air Greenland to inquire how they prepared for their 757 operations there. I don't have his reply handy; it is somewhere on a hard drive around here somewhere. But in any event, if I recall correctly, he said that it was a required simulator check item, and that it was not uncommon for pilots to fail that item and require re-training.

My analysis of using this airport as an alternate is below; I based it on the engine-out condition that would be a worst-case scenario requiring diversion to BGBW. Of course, we would have been doing this at night... :roll eyes:

Note: this was prepared ten years ago. I don't know what might have changed...so, obviously, NOT FOR USE IN NAVIGATION applies!

"There is only one instrument approach that is usable for 757 aircraft at Narsarsuaq. This is the NDB DME-1 to runway 7. This approach requires an MDA of 1800 feet for category C aircraft, and defines the MAP at 4.0 miles from the NDB DME. The runway is one mile closer, thus requiring a descent gradient of 5.66 degrees from the MAP to landing. This will require a descent rate of 1200 fpm at 120 knots of groundspeed. There is no way to consider this descent as a stabilized approach under standard guidelines, including our own FOM.

In the event of a missed approach, a minimum climb gradient of 4% is required. This gradient assumes that a missed approach is initiated at the MAP.

In section 4.12 of the 757-2Q8 Airplane Flight Manual, the flaps 20 approach climb chart indicates that, at a weight of 185,000 lbs and with engine and wing anti-ice on, the climb gradient will be 6.75%. A further reduction to 6.25% is required for ice accumulation on the airframe. Thus, from the MAP, a missed approach is feasible.

However, the same approach allows an MDA of 1500 feet for category A and B aircraft. In this case, the minimum climb gradient in the missed approach is 6%. Thus, it is reasonable to assume that, somewhere shortly after the MAP while descending to land, a 757 with one engine inoperative and ice on the airframe will quickly cross a point at which the minimum climb gradient could not be achieved. Further, the missed approach procedure is predicated in initiating the miss at the MAP.

An additional point is that all turns in the missed approach, initiated at the MAP, must be limited to 160 knots. It is reasonable to assume that, after the MAP, a slower speed would be required. However, we have no information on this."

Really interesting guys.....so it sounds like they used to do the NDB 5.6 degree glide approach (not some visual manoeuvre) with flap 20 and speedbrake (is flap 20 full flap on a 757). What would have been there IAS at a typical landing weight?

Apparently you can get a 787-800 in there
 

Flying over it yesterday and the FMC seems to think it could cope with the glide angle (but not the go around gradient). The Performace suggests that at 185,000 tons with a five knot tailwind Max Autobrake would stop you going off the end. Still suspect you would need speedbrake to prevent acceleration down the slope?

Must be one of the heavyweight 737s!


In reply to a previous post, full flap on the B757 is Flap 30. F20 is used for single-engined landing and for 2-E go-around.

It's a while ago, but I seem to remember a limit on how much flap is permitted (or recommended) with speedbrake - was (is?) it less than F20?

Flew both 737Classics, and Fokker 50 into Narssarsuaq. Would love to take a 757 in there. Coming down the glacier for a visual approach to runway 25, great fun.

WX usually clear cut, go or no-go. Majority of my landings there were in great weather.
NDB into 07, a little steep after the MaPt, but usually visual before and a slight dogleg would allow a lesser gradient.

The 757 can use speed brakes up to flaps 20.

I've seen videos going into BGBW that echo oceancrosser's recollections. In the daylight with good visibility, it looks spectacular.

However, there is a world of difference between using it as a primary destination and as an engine-out diversion alternate!

I was in a 787 - which also has a "soft" restriction of flap 5 for speedbrake .....so would be interested if any 757 guys could confirm that flap 20 and speed brake is not a combination Boeing routinely support?

..Flown the 757 into BGBW a few times..On NDB descend from FAF, reaching overhead the airport a left pattern visually, if runway in sight..Straight in landing not possible..

Was the straight in landing not possible because you would be unstable due to glide angle? Could you confirm what has been said about the speedbrake / F20 and whether this was a normal 757 technique?

..Sorry I do not recall the speedbrake / flap limitations anymore..Maybe a current 757-driver could help us ??..The straight in landing was not possible due to the steep descend angle requirements, therefore a circling approach from overhead the runway was made, to lose the altitude..Similar procedure used at some other airports surrounded by mountains..

Everyone mentioned F20 + speed brake. No-one included gear down. I hope it was; it's a big help (smile). It's been too long since B757, but if F20 speed brake UP is allowed is that better than F30 speed brake DOWN?