Below the GS at SFO again

[West Coast]

A 100 ft difference (if accurate) at the bridge isn't the difference between a stable and unstable approach. There's larger issues if you can't lose an extra 100 ft that far out.

[bubbers44]

I heard they were at 400 ft over the bridge so guess we are not talking about 100 ft.

[bubbers44]

They obviously need some flying lessons because any US pilot would look out his window and say what am I doing at 400 ft 6 miles out.

[Capn Bloggs]

what am I doing at 400 ft 6 miles out

Not quite that low, Bubba. They were 600 feet at 3.8 miles.

Is it really safer? 1900' at the bridge puts you above the PAPI. 1800' is closer to being on the PAPI.

The bridge is about 5.2nm from the threshold. Given the PAPI on 28L is 2.85°, on-slope would be about 1540ft. So we are now at 1900ft (350ft-odd high) with the PAPI showing 4 whites, with less than 2 minutes to get down to be stable by 1000ft AGL (assuming). What's going to happen? They are going to stuff the nose down. I suspect that in all the hullaballoo, they forgot to pull back when they got on-PAPI.

They should have coped but it appears the system set them up.

[olasek]

1540ft. So we are now at 1900ft (350ft-odd high)

Your calculations are seriously OFF, it was calcuted before, it is not 1540 but 1740 instead, this is how high you would be crossing the bridge shooting the ordinary ILS to 28L, so at 1900 you are only 160 ft higher, nothing that even a rookie commercial pilot could not handle. From the bridge it is 5.4 nm to the touchdown zone and the GS is at 3 deg. and the trigonometry is very easy. Also the Asiana 777 crew was nowhere near 1900' when crossing the bridge, they were at about 2400' so the system did not 'set them up', if there was any 'set up' here it was of their own making. Also your assumption about stability at 1000 ft is wrong, in VMC you can get stable as far down as 500 feet. Lets dispell any myth that this was a difficult approach, comparing with what's out there in the world of aviation it doesn't even qualify as a moderately difficult approach.

[BOAC]

bubbers/bug smasher - you have both failed to explain why a greater separation is required on a visual approach against that required on the other two. All three may be flown (and no doubt are) in VMC. (The visual glideslope is 2.85 degrees, by the way, (VGSI) so 1540'ish at the bridge would be correct. and would obviously conflict with San C, but why make it 1900?)

The whole thing sounds like a 1960's Haight-Ashbury put together.

[bubbers44]

I agree. I have done lots of approaches to 28L with no ILS and it isn't even worth talking about. It is so easy. Just look out the window and line up. Any private pilot could do it easily.

Automation has made pilots into monkeys. Not all pilots, just some who need automation because they can't do a simple visual approach without it.

[bubbers44]

I think any competent pilot could be 3,000 ft at the bridge and be stabilized at 500 ft so being a bit high should not be a problem unless you have a problem flying. 1900 ft at the bridge is a non event.

[Lord Spandex Masher]

Originally Posted by bubbers44

They obviously need some flying lessons because any US pilot would look out his window and say what am I doing at 400 ft 6 miles out.

I love your unwavering belief that any US pilot is infallible. I wonder why any US pilot would allow themselves to get to 400' at 6 miles?

[bubbers44]

LSM I don't think any pilot on earth would be at 600 ft 6 miles out and look out his window and think that looks about right. I will keep descending. Do you?

[Cows getting bigger]

Or indeed why any US pilot would slam a nosewheel into a runway? There are people on here who talk as if we should still be sky gods, capable of wrestling victory from defeat, rather than recognising the harsh reality that we are merely part of a system. Sure, if the Korean guys need their parts feeling for aspects of their airmanship then so be it, but let us not lunge at this as the only causal/contributory factor.

[BOAC]

LSM - what these gallant superb aviators cannot understand is that - shall we assume that it would be 'nice' to be stabilised on the visual g/slope at 1000' keeping all FOQA readers happy? - to achieve this but to be at 1900 at 5.2 from touchdown requires a rate of descent of almost 1300fpm or almost twice the correct rate.

The whole thing could be made far better if the VGSIs were at 3 degrees and 1800' at the bridge was 'standard', when I reckon 900fpm would crack it - and is far more 'acceptable' in FOQA terms and for 'seaparation' on g/a traffic.

I think we should quietly leave Bubbers in his own happy world at 3000' at the bridge....

[bubbers44]

We did th 3,000 ft outer marker into SJC for decades with no problem with our 737's. It was a noise abatement arrival that all of us did with no problem. It would be even easier into 28L at SFO with the long runway. The physics was about the same. Idle power until 500 ft which went away about 10 years ago.

[rudderrudderrat]

Hi BOAC,

shall we assume that it would be 'nice' to be stabilised on the visual g/slope at 1000' keeping all FOQA readers happy? to achieve this but to be at 1900 at 5.2 from touchdown requires a rate of descent of almost 1300fpm or almost twice the correct rate.

Even that is well within the guidance of our FCTM when doing an ILS in IMC.
So it certainly is not a problem when visual.
"GLIDE SLOPE INTERCEPTION FROM ABOVE
The following procedure should only be applied when established on the localizer. There are a number of factors which might lead to a glide slope interception from above. In such a case, the crew must react without delay to ensure the aircraft is configured for landing before 1 000 ft AAL.
In order to get the best rate of descent when cleared by ATC and below the limiting speeds, the crew should lower the landing gear and select CONF 2. Speedbrakes may also be used, noting the considerations detailed in the sub-section "Deceleration and configuration change" earlier in this chapter. When cleared to intercept the glide slope, the crew should:
• Press the APPR pb on FCU and confirm G/S is armed.
• Select the FCU altitude above aircraft altitude to avoid unwanted ALT*.
• Select V/S 1500 ft/min initially. V/S in excess of 2 000 ft/min will result in the speed increasing towards VFE"

[BOAC]

Bubbers - things have changed a bit. The emaphasis now is on steady, measured flying as an aim.

RRat - it was not in the 737 FCTM in my time, but a 'special brief' was required if more than 1000fpm was required.

I still cannot understand why SFO has done it this way when 1800 and 3 degrees would make life a lot easier..

[Auberon]

As they said in school, show your work.

The 28L extended centerline crosses the bridge at approximately 37°34'21.00"N,122°15'49.20"W.
http://goo.gl/maps/sC6la

The 28L displaced threshold is at approximately 37º36'43.54"N,122º21'33.35"W.
http://goo.gl/maps/xJP48

The distance between those two points is approximately 31,227 feet.
Great Circle Mapper

The 28L PAPI has a 2.85º glide path and a TCH of 64 feet, so add 1,286 feet to get the touchdown point.
64/tan 2.85º - Wolfram|Alpha

So we have 32,513 feet between the bridge and the touchdown point.
31227+1286 - Wolfram|Alpha

That means to be on the PAPI at the bridge you would cross at 1,619 feet.
32513*tan 2.85º - Wolfram|Alpha

[DOVES]

To BOAC

to achieve this but to be at 1900 at 5.2 from touchdown requires a rate of descent of almost 1300fpm

Probably I did not understand correctly
But I would like to point out humbly that:
With 120 knots to lose 1900 ft in 5.2 NM a variometer of a little more than 730 ft/min is needed, with 150 knots 760 ft/min.

[BOAC]

Originally Posted by BOAC

shall we assume that it would be 'nice' to be stabilised on the visual g/slope at 1000' keeping all FOQA readers happy?

- ie not threshold.

[bubbers44]

BOAC, Please don't worry so much because when you retire it doesn't matter if it is 2.85 or a 3 degree glide slope. You can intercept a glide slope from either above or below. Who cares what the new hire qualifications are. You won't have to fly with them. Just kick back and enjoy life.

[BARKINGMAD]

ENERGY MANAGEMENT (YET) AGAIN?

Is it not up to us airframe managers to have the cohones to say to ATC;

"Regret, unable due energy management" when invited/instructed to place our craft in a potentially UNSTABLE approach, a proper response to which is usually enough to permit a more measured and controlled manoeuvre?

So why are we not doing so?

There are a large number of "cowboy" airframe managers out there who regard that as "cissy" and the "we can hack it" attitude seems to be reflected in the spate of overruns at worst or FDM events at best.

Maybe the HR wallahs could be invited to throw away their useless psychometric tests and search for a more reliable testing method to exclude these dangerous characters, possibly before the insurers force them to??

Similarly, training departments and staff should be up to the mark when they are asked for guidance on the subject of E M, a subject which is so sadly neglected or is liable to a variety of methods which only serve to confuse.

My recent conversations with "newbies", otherwise very well-prepared for the line, shows this essential aspect of flying is either not taught well, badly imparted or a confusing variety of methods of (mentally) computing and managing the problem just makes life more difficult and liable to error.

Furthermore, the majority of these "rules of thumb" only refer to the combination of potential (altitude) energy, (kinetic) speed energy, of aircraft and (occasionally) the instantaneous wind velocity. None I have heard of include the weight (sorry, mass!) of the 'frame, which can have a significant effect on the trackmiles required to dissipate this energy, hopefully in an efficient, quiet, smooth and fuel-cheap manner.

Proof of the "m" effect on the 1/2mV squared part of the total is hidden away in the OMs various contained in the EFB or in the drawer beneath the jumpseat in the "NG", sadly it has recently been removed from the QRH Performance Inflight (in my current company), where it should be readily available on a sector by sector basis, especially for the "newbies" as they get to grips with the job.

I suspect that some of the "oldies" are not aware of this significant factor either, but I place the blame fairly and squarely in the hands of the relevant TRTOs.

Rant over, I really must get out more...............................................