Pakistan plane crash: Jet carrying 107 people crashes into houses near airport

[Evan]

ALSO, if you want to save gas, you do NOT descend fast...(but perhaps that concept is too much for them)

I think they might be referring to the CI (cost index) which considers both the cost of fuel and the cost of operating time. The optimum savings is found between a CI of zero (best fuel economy) and whatever the max is for the aircraft (least operating time).

But fuel conservation methods include minimizing flight time at low altitude and delaying flaps, both of which can be done (but should never be done) by remaining 'hot and high' and then coming down steep at flight idle, arresting with speed brakes and getting out landing flaps and gear as late as possible. But this is the definition of an unstable approach.

Besides the danger this poses to life and limb (and airframe), such technique also elevates the odds of a missed approach. According to one Boeing article I recall, go-arounds can use between 2 and 28 times more fuel than a stable, by-the-book approach, so only over-confident, high rolling cowboys would ever choose this technique.

Considering the pressure PIA was allegedly placing on CI, a go-around would tend to be resisted until the last minute, or resisted altogether.

Homicidal culture.

[3WE]

arresting with speed brakes and getting out landing flaps and gear as late as possible

You really need to study up on some fundamental stuff.

It seems that extreme focus on rote memorization of acronym checklists might miss some important stuff.

[ATLcrew]

But fuel conservation methods include minimizing flight time at low altitude and delaying flaps, both of which can be done (but should never be done) by remaining 'hot and high' and then coming down steep at flight idle, arresting with speed brakes and getting out landing flaps and gear as late as possible.

None of my three airlines preached such a thing.

[Evan]

None of my three airlines preached such a thing.

How many of them were based in Pakistan?

[Evan]

None of my three airlines preached such a thing.

If the approach is not being conducted in adverse conditions that would make it difficult to achieve stabilized approach criteria, the final flap selection may be delayed until just prior to 1,000 feet above field elevation (AFE) to conserve fuel and reduce noise and emissions or to accommodate speed requests by air traffic control. This approach is known as a low‑drag, delayed-flaps, or noise-abatement approach. Note: The thrust required to descend on the glide slope may be near idle.

Also, one of their seven tips:

5. Avoid flying extended periods at low altitudes.

Now misinterpret that in the mind of a cowboy airman trying to please a penny-pinching boss in the absence of a functional safety culture.

- Stay at higher altitudes as long as possible.
- Descend with open descent mode, i.e. thrust at flight idle. Moderate speed with elevators and speedbrakes.
- Compress the flap schedule as close to landing as possible.

Now look at the actual approach profile of PIA 8303. Flaps 1 comes out less than 6nm from the runway and well over placard speed. He intercepts the GS at about 5nm but then gets a bit high again. He goes directly to flaps 3 at about 1500ft, again, well over placard speed. At 1nm out he is actually on the GS but has failed to manage speeds, configure the aircraft or complete the checklists. So too fast, not properly configured and, whoops, no gear.

8303 went from FL350 to the runway in about 18 mins. That seems to me to mean they delayed TOD by about 12mins. Why?

Makes me think there is a practiced technique here that didn't go so well this time.

Of course no airline with a valid safety culture would ever preach such a thing. But an airline that preaches skimping on fuel above all else is essentially preaching such a thing.

[3WE]

None of my three airlines preached such a thing.

I am struggling with Evan's ever present black and white mentality and how a few key adjectives totally flip the scale.

Jet Fuel used to be expensive and fuel savings were "of interest."

No doubt that can do some things to save fuel in how you operate.

That being said, somehow you are able to not_be stupid about it (maybe you are a genius and indeed you are not_Pakistani?)

A well planned descent without the use of spoilers (and NO need for excess speed)...Indeed it's good to not_be UNNECCESARILY dragging all over creation at low altitudes with full flaps and wheels out...If it works with ATC, (and again, you are not_stupid about it) kudos for you for protecting us from additional global warming....

But alas, I need to stick to cow farts and non-synthetic nitrogen sources.

[kent olsen]

Interesting. I flew 3 transport aircraft, DC-9, DC-8 (60/70 series), B-747 for two different airlines and we always descended at idle. That gave you about 2500-3000 fpm descent. Then I flew the Hawker 1000 and Citation X and you had to use a little power or you'd come down at over 3000 fpm. Basically ATC starts all jets down at the same distance out. Big jets can do that at idle, smaller ones need a little power to control it.

[Evan]

Basically ATC starts all jets down at the same distance out. Big jets can do that at idle, smaller ones need a little power to control it.

Yes but this one appears to have started down about 10 minutes late, perhaps intentionally. Correct me if I'm wrong but wouldn't the descent normally be initiated around 09:05 on the chart shown below?

I went through a few altitude graphs on FlightRadar24 showing AIrBlue A320 flights descending into Karachi. The descent/landing times from around FL350 were between 25 and 30 mins. PK8303 did it in about 18 mins.

Question is: could that be part of a flawed fuel conservation strategy to minimize flight time at low altitude?

[3WE]

Question is: could that be part of a flawed fuel conservation strategy to minimize flight time at low altitude?

Fast descents do not save fuel.

I guess that does make it a flawed strategy.

[Schwartz]

There WAS a big focus on optimizing landings to conserve fuel, but right now that is out the window. But it will come back. I suspect you might be surprised at what type of approach is the most efficient. It probably means small changes in thrust, not zero and then max thrust.

[Gabriel]

The most fuel-efficient feasible approach is one where you go from cruise altitude and cruise speed smoothly to 2500ft ARL and ~200 KIAS some 10 miles short of the runway, all the time at idle and with the airplane clean, you then have ~ 2 minutes (still at idle) to slow down to final approach speed as you progressively extend slats/flaps and gear and then, with the plane fully configured for landing, for the first time since you started the descent, increase thrust from idle to keep the approach speed and thus finally stabilize the approach, and complete the landing checklist as you arrive to the 1000 ft gate some 3 NM from the runway threshold.

There are crazier more efficient alternatives, but they are too crazy and the fuel gain is negligible compared to the one above.

[Evan]

The most fuel-efficient feasible approach is one where you go from cruise altitude and cruise speed smoothly to 2500ft ARL and ~200 KIAS some 10 miles short of the runway, all the time at idle and with the airplane clean, you then have ~ 2 minutes (still at idle) to slow down to final approach speed as you progressively extend slats/flaps and gear and then, with the plane fully configured for landing, for the first time since you started the descent, increase thrust from idle to keep the approach speed and thus finally stabilize the approach, and complete the landing checklist as you arrive to the 1000 ft gate some 3 NM from the runway threshold.

There are crazier more efficient alternatives, but they are too crazy and the fuel gain is negligible compared to the one above.

Indeed, but we are dealing with crazy here. It would seem to me, if I place no value on safety (or the heightened possibility of a missed approach), that the most cost-efficient alternative (remember, the target is the best CI, a compromise between fuel conservation and operating time) would be to cover more distance in less time at cruise where the engines are most efficient and then to do the entire descent including most of the final 3nm at idle while having minimum drag out for as long as possible. Would you agree?

[3WE]

On most of my airliner flights in good weather, full flaps are selected way past the outer marker...Thus making for a much shorter stabilized approach and a potential reduction in safety.

Seems to me we need to ban all airplanes and publicly beat most pilots.

[3WE]

Indeed, but we are dealing with crazy here. It would seem to me, if I place no value on safety (or the heightened possibility of a missed approach), that the most cost-efficient alternative (remember, the target is the best CI, a compromise between fuel conservation and operating time) would be to cover more distance in less time at cruise where the engines are most efficient and then to do the entire descent including most of the final 3nm at idle while having minimum drag out for as long as possible. Would you agree?

Put whatever you want in the rule book...

It won't replace fundamental knowledge, nor will it change the fact that ATL said this was a slightly-challengly-steep approach.

Are there any checklist items to check that the landing gear are down?

[Gabriel]

ATL said this was a slightly-challengly-steep approach.

Where? Post # please?

Why do you insist with just the gear issue? They crossed the threshold at 210kts overspeeding the flaps. CLEARLY and UNDOUBTEDLY (yes black and white) the gear was not the ony issue here. Even if they had lowered the gear and gotten away with it, this would have been very very VERY bad airmanship worth of immediately firing both pilots and revoking their licenses for life (again, yes, black and white) (although that would have never happened because no one outside of the airline would have know it and the airline was encouraging this behavior).