QF32 by Richard De Crespigny
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QF32 by Richard De Crespigny
I recently read the book QF32 by Richard De Crespigny who piloted the crippled Qantas A380 from Singapore in 2010. There were some technical points he made that I didn’t fully understand which I’ve outlined below, perhaps someone could clarify them for me please:
1) On p135 he writes:
“You might think this unbelievable, but some of the basic navigation techniques we used in the Caribous in the 1980’s still come in handy on the A380. Although there are many radar systems that can predict whether the aircraft will travel over and clear the tops of a thunderstorm, pilots don’t fully trust any of them, and the Earth’s curvature and cloud distorts your view, making it hard to know if you will overfly the cloud that lies ahead. In the Caribou, we held a glass of water in front of our eyes and skimmed our eyesight over the top of the water’s surface. This was a simple technique to find a level but it worked, and this trick is still used in the A380 – although a large 2 – litre plastic water bottle delivers a much more reliable horizon!”
Not sure how this works. My guess is that the water surface being flat, if you look across the top of it from the side and can see the impending cloud tops above this water level then they’re higher than your current altitude? Is that right?
Has anyone actually used this technique, is it feasible to do this in a bouncy cockpit due to turbulence?
2) On p198 he talks about a “fuel gravity ceiling”, what is this limitation? This implies there is an altitude above which gravity feed alone doesn’t work?
3) On p202 he writes:
“It was now my turn. I reasoned that perhaps a metal chip detector in the hydraulic system has detected iron filings in Engine 4’s pumps; that is in this case Engine 4 might take out Engine 3’s hydraulics, and so I suggested we turn off pumps 5 and 6 to preserve pumps 7 and 8. Everyone quickly gave a thumbs-up.”
I understand that the hydraulic system on the Right wing goes through all 4 pumps so if metal chips were detected in Engine 4’s pumps (that is 7 & 8) then it’s too late and they will have contaminated the whole fluid system. Also the cause of the chips may not necessary have originated in pumps 7 and 8 but possibly in pumps 5 and 6?
4) On p249 he writes:
“Both outer ailerons and one mid aileron were unpowered and slipstreaming in airflow – at about 80 per cent full up! In addition, at least one spoiler was also unpowered and raised into the airflow.” There’s even a photo taken of the left wing showing both these ailerons and spoiler in this elevated position in the 2nd lot of photos in the book between pgs. 278 and 279.
Why would a control surface stick out into the airflow if it was essentially freely hinged? Was there some residual force pushing it up (e.g. a spring?) that is normally counterbalanced by the hydraulic pressures which were now lost? Or was it due to the higher pressure under the wing pushing it up?
5) On p262 he writes:
“At a fraction of a second before I sensed the landing gear crashing down onto the runway – I pushed the side-stick full forward. …………….
As the nose lowered, the wheels behind the centre of gravity rose, and the aircraft’s rate of descent reduced as the plane settled onto a pillow of air trapped between it and the tarmac (a phenomenon pilot’s call Ground Effect). The fast descent rate washed off. Nancy-Bird cushioned onto the runway and we touched down at only two and half feet per second.”
I understand by pitching the nose down the main wheels behind the CoG will go up (as the whole aircraft rotates about its CoG) and this would reduce the wheels own individual descent rate relative to the runway but this manoeuvre will not reduce the aircrafts overall descent rate (as measured at its CoG). If anything it will increase it by reducing the angle of attack. Surely the ground effect can’t be that powerful? He’s saying the RoD was reduced from 14 ft/s to 2.5 ft/s due to this manoeuvre. Correct me if I’m wrong but I would have thought the maximum RoD limitation is based on the whole aircraft and the energy the oleo’s have to absorb, not what particular descent speed the main wheels are doing when they hit the tarmac?
Surely if the ground effect were that powerful it would mean that for a normal landing where you flare the aircraft it would float along the runway for a considerable distance.
6) During promotion of the book a lot was said about the Captain using the “Heading Alignment Cone (HAC)” technique used by the Space Shuttle for its glide landings but there was virtually nothing mentioned in the book to explain this other than a diagram given in the photos between pgs. 278 and 279. From this diagram I get the impression it’s basically about keeping within an imaginary cone centred on the destination airfield to be able to glide to it safely while making a continuous 270 turn. Is this basically the HAC procedure?
thanks in advance for any responses.
1) On p135 he writes:
“You might think this unbelievable, but some of the basic navigation techniques we used in the Caribous in the 1980’s still come in handy on the A380. Although there are many radar systems that can predict whether the aircraft will travel over and clear the tops of a thunderstorm, pilots don’t fully trust any of them, and the Earth’s curvature and cloud distorts your view, making it hard to know if you will overfly the cloud that lies ahead. In the Caribou, we held a glass of water in front of our eyes and skimmed our eyesight over the top of the water’s surface. This was a simple technique to find a level but it worked, and this trick is still used in the A380 – although a large 2 – litre plastic water bottle delivers a much more reliable horizon!”
Not sure how this works. My guess is that the water surface being flat, if you look across the top of it from the side and can see the impending cloud tops above this water level then they’re higher than your current altitude? Is that right?
Has anyone actually used this technique, is it feasible to do this in a bouncy cockpit due to turbulence?
2) On p198 he talks about a “fuel gravity ceiling”, what is this limitation? This implies there is an altitude above which gravity feed alone doesn’t work?
3) On p202 he writes:
“It was now my turn. I reasoned that perhaps a metal chip detector in the hydraulic system has detected iron filings in Engine 4’s pumps; that is in this case Engine 4 might take out Engine 3’s hydraulics, and so I suggested we turn off pumps 5 and 6 to preserve pumps 7 and 8. Everyone quickly gave a thumbs-up.”
I understand that the hydraulic system on the Right wing goes through all 4 pumps so if metal chips were detected in Engine 4’s pumps (that is 7 & 8) then it’s too late and they will have contaminated the whole fluid system. Also the cause of the chips may not necessary have originated in pumps 7 and 8 but possibly in pumps 5 and 6?
4) On p249 he writes:
“Both outer ailerons and one mid aileron were unpowered and slipstreaming in airflow – at about 80 per cent full up! In addition, at least one spoiler was also unpowered and raised into the airflow.” There’s even a photo taken of the left wing showing both these ailerons and spoiler in this elevated position in the 2nd lot of photos in the book between pgs. 278 and 279.
Why would a control surface stick out into the airflow if it was essentially freely hinged? Was there some residual force pushing it up (e.g. a spring?) that is normally counterbalanced by the hydraulic pressures which were now lost? Or was it due to the higher pressure under the wing pushing it up?
5) On p262 he writes:
“At a fraction of a second before I sensed the landing gear crashing down onto the runway – I pushed the side-stick full forward. …………….
As the nose lowered, the wheels behind the centre of gravity rose, and the aircraft’s rate of descent reduced as the plane settled onto a pillow of air trapped between it and the tarmac (a phenomenon pilot’s call Ground Effect). The fast descent rate washed off. Nancy-Bird cushioned onto the runway and we touched down at only two and half feet per second.”
I understand by pitching the nose down the main wheels behind the CoG will go up (as the whole aircraft rotates about its CoG) and this would reduce the wheels own individual descent rate relative to the runway but this manoeuvre will not reduce the aircrafts overall descent rate (as measured at its CoG). If anything it will increase it by reducing the angle of attack. Surely the ground effect can’t be that powerful? He’s saying the RoD was reduced from 14 ft/s to 2.5 ft/s due to this manoeuvre. Correct me if I’m wrong but I would have thought the maximum RoD limitation is based on the whole aircraft and the energy the oleo’s have to absorb, not what particular descent speed the main wheels are doing when they hit the tarmac?
Surely if the ground effect were that powerful it would mean that for a normal landing where you flare the aircraft it would float along the runway for a considerable distance.
6) During promotion of the book a lot was said about the Captain using the “Heading Alignment Cone (HAC)” technique used by the Space Shuttle for its glide landings but there was virtually nothing mentioned in the book to explain this other than a diagram given in the photos between pgs. 278 and 279. From this diagram I get the impression it’s basically about keeping within an imaginary cone centred on the destination airfield to be able to glide to it safely while making a continuous 270 turn. Is this basically the HAC procedure?
thanks in advance for any responses.
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Ground Effect
Ground effect is all about reduced downwash and (lift) induced drag:
Prandtls lifting line theory: CDi (induced drag) reduces to ~ 50% at 10% of the wingspan gnd clearance.
Weiselberger’s theory (graph) for a 747-400 (213’ wingspan), increased by 12’ for the winglets:
https://qf32.files.wordpress.com/2014/01/induceddrag_vs_alt.jpg
CDi is down to 50% in the flare! So an aircraft flared in ground effect will have significantly reduced total drag so will cruise to the end and beyond the end of the runway
The reduction in CDi explains why:
- Do not allow the airplane to float, fly the airplane onto the runway.
- Do not attempt to extend the flare by increasing pitch attitude in an attempt to achieve a perfectly smooth touchdown.
- Do not attempt to hold the nose wheel off the runway.
Prandtls lifting line theory: CDi (induced drag) reduces to ~ 50% at 10% of the wingspan gnd clearance.
Weiselberger’s theory (graph) for a 747-400 (213’ wingspan), increased by 12’ for the winglets:
https://qf32.files.wordpress.com/2014/01/induceddrag_vs_alt.jpgCDi is down to 50% in the flare! So an aircraft flared in ground effect will have significantly reduced total drag so will cruise to the end and beyond the end of the runway
The reduction in CDi explains why:
- Do not allow the airplane to float, fly the airplane onto the runway.
- Do not attempt to extend the flare by increasing pitch attitude in an attempt to achieve a perfectly smooth touchdown.
- Do not attempt to hold the nose wheel off the runway.
Last edited by 35YearPilot; 18th Apr 2017 at 14:44.
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Maybe some people just don't trust the horse's mouth nearly as much as a bunch anonymous screennames on the internet.
Loved the part about the 2-liter water bottle. I bet he carries a leather helmet and goggles in his bag, too.
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[QUOTE=Aviator_69;9742373]I recently read the book QF32 by Richard De Crespigny who piloted the crippled Qantas A380 from Singapore in 2010. There were some technical points he made that I didn’t fully understand which I’ve outlined below, perhaps someone could clarify them for me please:
He did a chapter on HAC but he talked about why he didn’t use it. 1) He didn’t have to and 2) The others voted him down on climbing to 10000 to instigate it if he had to.
He did a chapter on HAC but he talked about why he didn’t use it. 1) He didn’t have to and 2) The others voted him down on climbing to 10000 to instigate it if he had to.
Last edited by JoCam; 21st Apr 2017 at 01:29.
The real hero on that flight was the Check Captain Dave Evans. He prevented RDC from advancing the thrust levers to climb to 10000' for his Walter Mitty dreams of an Armstrong spiral!
As for the water bottle technique of working out if you're going over a TS, why are you going over the top of a TS when you should be going around it? If the cloud continues to move up your windscreen then you are going through it and if it moves down your windscreen then you are going over it.
As for the water bottle technique of working out if you're going over a TS, why are you going over the top of a TS when you should be going around it? If the cloud continues to move up your windscreen then you are going through it and if it moves down your windscreen then you are going over it.
The water bottle. Recall reading an article, by noted aviator and author Len Morgan I think it was, who talked about carrying a small spirit level in his bag to see if he would top the clouds ahead. Don't recall an explanation as to why, perhaps consideration as to possible use of anti ice.
Chesty,
"Spoilers do float as a result of the process for making lift."
Ok you got me, considering spoilers are designed to "spoil" lift over the wing and on the A380 they are operated by 5000psi hydraulics to keep them up/down. How do they "float" against that pressure in a fully serviceable spoiler system?
"Spoilers do float as a result of the process for making lift."
Ok you got me, considering spoilers are designed to "spoil" lift over the wing and on the A380 they are operated by 5000psi hydraulics to keep them up/down. How do they "float" against that pressure in a fully serviceable spoiler system?
PPRuNe Handmaiden
I've done the water bottle trick. It doesn't replace the weather radar etc but it is fun.
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Chesty,
"Spoilers do float as a result of the process for making lift."
They don't. However, in the OP, it was stated that one spoiler was unpowered.
Ok you got me, considering spoilers are designed to "spoil" lift over the wing and on the A380 they are operated by 5000psi hydraulics to keep them up/down. How do they "float" against that pressure in a fully serviceable spoiler system???
McHale.
"Spoilers do float as a result of the process for making lift."
They don't. However, in the OP, it was stated that one spoiler was unpowered.
Ok you got me, considering spoilers are designed to "spoil" lift over the wing and on the A380 they are operated by 5000psi hydraulics to keep them up/down. How do they "float" against that pressure in a fully serviceable spoiler system???
McHale.
They don't. However, in the OP, it was stated that one spoiler was unpowered.
There was a time when challenging someone went something like 'Oh, right I didn't know that, how does that happen?'
In the mists of time I think.
Spoiler float.
https://www.federalregister.gov/docu...pany-airplanes
Incident
http://rnsa.is/media/1172/final-repo...ary-2013-1.pdf
Boeing requested that we revise the Discussion section of the NPRM to clarify that “spoiler panel float” occurred when there was a hydraulic system pressure loss, and that when the flaps were extended beyond 20 degrees, the spoiler panel float became severe enough to adversely impact airplane control. Boeing explained that spoiler float will occur at all flap detents in the presence of a failed hydraulic system and a compromised spoiler actuator. Boeing explained that the magnitude of the spoiler float angle at the flap detents of 20 degrees and below is relatively modest and results in a rolling moment that is well within the airplane's capabilities to offset. Boeing stated that when a flap detent greater than 20 degrees is selected, the magnitude of the spoiler float angle increases dramatically, and the float angle becomes large enough to reduce the margin of airplane control authority.
Incident
http://rnsa.is/media/1172/final-repo...ary-2013-1.pdf
Last edited by megan; 30th Apr 2017 at 04:08.
