QF 737 to break sound barrier!

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dcauson

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Nov 17, 2011
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Flew MEL-PER on QF 777 last night.

Flight was completely full, not a seat spare. Just as the FAs were closing up the doors the pilot came on the horn to explain the half hour delay to departure. Due apparently to the fact the aircraft had come into T2 in Melbourne and needed to be towed to T1, blah blah blah.

Then came the good bit. All was OK!. We would make up time as they were going to put extra fuel ("gas") in the plane and fly at a lower altitude (32000 feet) so they could power up the engines with the extra fuel on board and make the plane go faster!

A bit concerning a Qantas pilot isn't aware of basic aerodynamics and that air speed is not really something you can just speed up with a bit of extra engine power and doing so would be dangerous as we would have to breach the sound barrier to make up that sort of time. The extra fuel and lower altitude was more likely due to the heavy payload the aircraft was taking and increased drag at flying at such an altitude requiring the additional engine power and fuel.

Surely the pilot knew all this and was just a blatant lie that we would be flying faster, in which case why do so? Plane was only 10-15 minutes delayed for landing anyway, more due to the fact the schedule has some fat in it for stronger head winds. Seems like a pilot and co-pilot taking credit for something that is impossible, unless QF intentionally fly below cruising speed in their 737s routinely and have this option available to them, but wouldn't think so?
 
A bit concerning?

*Edit - There is an Ask the Pilot thread if you would like to ask someone who is qualified in this area (and yes I believe there is a 737 pilot on board who can provide an answer).

Ask The Pilot.
 
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I'm not so sure I'd quickly be able to do the maths you've highlighted and the pilot's announcement would probably make sense to most people on board.

Just another example of working to the lowest common denominator??

Regards,

BD
 
Flying lower to avoid the worst of the jet streams uses more fuel but also ensures a quicker flight time.
 
Ground speed is what matters in determining time from A to B. Ground speed between MEL and PER can be quite, umm, leisurely at times, so if flying a bit lower increases the ground speed, then all the better.

So lower altitude may have given them the same airspeed but a greater ground speed.
 
.....A bit concerning a Qantas pilot isn't aware of basic aerodynamics and that air speed is not really something you can just speed up with a bit of extra engine power .....

And it's not April Fool's Day?
 
Sounds like it’s time for you to dust off that ATPL. Wait you don’t have one. Well neither do I, but if you did the sensible thing and checked the flight data that’s available on flightaware, you’d have seen that the peak cruising speed was significantly higher on this flight than all other QF777 flights the past week. I’m not going to opine on aerodynamics and the basics of flight, but one thing I do understand is that keeping all else constant, increasing engine power will in fact increase speed. Can I ask why you think it’s dangerous to operate an aircraft within its performance limitations notwithstanding a higher than normal cruising speed?
 
Flew MEL-PER on QF 777 last night.

Flight was completely full

But that’s not how a pilot calculates the payload. The weight variables are passengers + luggage + freight + fuel

half hour delay to departure. Due apparently to the fact the aircraft had come into T2 in Melbourne and needed to be towed to T1, blah blah blah.

Yes - the joys of commercial aviation. “Blah blah blah” - yes we have all heard the reasons before and some. And some and more believable than others. But it is what it is.

We would make up time as they were going to put extra fuel ("gas") in the plane and fly at a lower altitude (32000 feet) so they could power up the engines with the extra fuel on board and make the plane go faster!

These are 2 separate items combined into one.
Fly lower = more drag = extra fuel.
But the reason to fly lower would have to gain some advantage from predicted winds. The airline has accurate meteorological informationZ
Fly faster = more fuel per km
So add more fuel and fly faster if the want!!

A bit concerning a Qantas pilot isn't aware of basic aerodynamics
I’m sure pilots of this airline are pretty good at aerodynamics and they have computers with Boeing software that allows them to calculate all sorts of performance data.

and that air speed is not really something you can just speed up with a bit of extra engine power and doing so would be dangerous as we would have to breach the sound barrier to make up that sort of time.
I’m pretty sure by pushing the throttles forward the aircraft will accelerate. After all isn’t that how the aircraft is able to take off?. By going fast enough that wings provide a lift vector?
Breach the sound barrier?. Did you know the sound barrier is not actually a barrier?. Anyway did you take into account in your calculations that speed of sound varies with temperature? What was the actual fastest indicated airspeed of your flight?



The extra fuel and lower altitude was more likely due to the heavy payload the aircraft was taking and increased drag at flying at such an altitude requiring the additional engine power and fuel.

Why do you think the airplane was carrying a heavy payload?. What was the actual payload? Maybe it was light because it was not carrying much freight?.


unless QF intentionally fly below cruising speed in their 737s routinely and have this option available to them, but wouldn't think so?
And what cruising speed is that. The faster the flight the shorter the flight but more costly in terms of extra fuel and engine wear. But the aircraft can fly higher. The slower the flight the lower the max altitude so might have to fly at lower altitude. Flying slower might mean you arrive at approach late and then have to be in a holding pattern. flying faster might do the same too

There is an efficient speed which is more complicated than just a cruising speed.

Come joins us at the Ask the Pilot thread. I’m not a pilot but have learnt and gained much insight from helpful aviators
 
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I use to fly jets for a living, just in case the original poster wasn’t intending this as a wind up here’s a couple facts:
1. At Mach 0.78 the aircraft is flying well short of reaching any sound barriers, speeding it up by .01 ain’t going to be anything close
2. Airliners are flown at a cost index speed well below their maximum operating speed (fuel efficiency for the bean counters) - popping on some extra fuel to increase the thrust and flying lower in the thicker air certainly gives the pilots the option of speeding things up
3. The higher you fly (in particular right up above 38000ft where a Perth flight will be) the more limiting your options become due to thin air, there is a very small margin between your maximum operating speed and the minimum speed the aircraft can fly at - going lower increases those options
4. A normal MELPER flight won’t be anywhere near maximum takeoff weight unless it’s carrying a lot of reserve fuel due to poor weather in Perth- the aircraft is nowhere near it’s maximum range on that route.

I guess all those years I spent studying aerodynamics helped :)
 
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