C-FWGH 738 slow take off BFS : AAIB
But no pilot should be content to attempt to takeoff with <90%. That's gut feeling at least; surely. nd it's 2 pilots who stopped thinking, not just one
With low experience pilots poor management of workload ( rushing) often means that common sense cross checks are simply not done, the data is simply accepted. With more experienced crew rushing is also a problem but being dog tired is a more likely culprit for not trapping what is an easy error to make.
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TOC OAT, airfield OAT - entering these into the FMC = 
about with trivia. There can be no measurable upside to it but there certainly is a downside - you get bogged down with this crap and lose objectivity.
about with trivia. There can be no measurable upside to it but there certainly is a downside - you get bogged down with this crap and lose objectivity.
My proposal was published in the nascent International Journal of Air Safety about 1982. With current avionics it should be easily attainable, another gap plugged. Haven't forgotten the Emirates near disaster at Melbourne some years ago as a result of T/O calculations being based on weight 100 t below actual.
We DID have an acceleration check to 100 knots on the V force (Valiants and Victors in my case) so was quite surprised that there was no such procedure when I came onto the VC10 in civil aviation.
If, as I believe, aircraft such as the 380 can warn crew that the intended runway is too short for the intended landing then an acceleration check system should be easy. Just a bug moving around the asi to show just what speed should be attained ar any point on the take off. Rather like the bugs on the Concorde ASI showing the required speed for the C of G position.
I still think it will come eventually.
Still remember briefing new pilots in my time as TC that if there is ANY doubt at all about TO acceleration with reduced thrust just push the levers to the stops, the engines will take it without any problem!
One of the training issues might be that it is largely impractical (and expensive) to demonstrate the feel of lack of acceleration in an actual airplane and while sims are wonderful these days it is not quite the "all enveloping" sensation. It is also possible that practical training for these events might cause more accidents than they save.
Back in the stone ages when I learned to fly spin training was, IIRC, mandatory. Eventually it was discontinued, as I understand it, because losses training were higher than losses from general flying and aircraft were being built more spin resistant. (I learned on a Colt, they were getting there!)
As a fairly frequent passenger I believe the "lack of airmanship" and "air sense" thing is a very real concern.
Back in the stone ages when I learned to fly spin training was, IIRC, mandatory. Eventually it was discontinued, as I understand it, because losses training were higher than losses from general flying and aircraft were being built more spin resistant. (I learned on a Colt, they were getting there!)
As a fairly frequent passenger I believe the "lack of airmanship" and "air sense" thing is a very real concern.
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I read this site cause it is after all in the public domain and I used to be a Cessna 152 weekend warrior so do have a tiny inkling etc etc.
In the above I used to find that firewalling the throttle would get me safely into the air.....
And now for the stupidest question ever asked on Pprune.
Why are the taps in comm jets not firewalled on take off to get them safely into the air?
In the above I used to find that firewalling the throttle would get me safely into the air.....
And now for the stupidest question ever asked on Pprune.
Why are the taps in comm jets not firewalled on take off to get them safely into the air?
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On turbine engines, using less than 100% power lowers hot section temperatures, greatly increasing engine life. In most twin-engine transports there is power to spare unless limited runway available.
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One of the training issues might be that it is largely impractical (and expensive) to demonstrate the feel of lack of acceleration in an actual airplane
The norm, at differing weights, is something you become used to every day. If you car is sluggish you realise it instantly.
The norm, at differing weights, is something you become used to every day. If you car is sluggish you realise it instantly.
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Honestly, is that really true? I have taken off safely with the correct performance in a 737NG with N1 values as low as 75%. It all depends on the conditions of course, and performance values can differ a lot, especially if you fly different variants.
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If the data supports it, then you should use whatever you can eke out. Trouble is, garbage in, garbage out. We sometimes need maximum available derate, particularly on low RCR fields (talking of below 5 here) in strong crosswinds, as the DRT gives us a much better Vmcg. Not to mention,you get airbourne much closer to Vmca/V2 on derate departures as your rotate speed is typically 10-15 knots higher, particularly at light weights.
might want to reconsidert that, particularly if Vmcg is based upon your derated thrust setting. you are going off the edge if you suffer a subsequent engine failure past V1 with a vmcg issue and max thrust now set.
This all comes down to airmanship and the likes of gross error checks/independent perf calculations. Not sure the typical loco turnaround times would support that though...
Reaction... before, or certainly past V1, we are now going flying. Lets apply full-power, manually (Firewall the trust levers) and get this aircraft into the air and climbing away. Sort out/discuss the cause later.
This all comes down to airmanship and the likes of gross error checks/independent perf calculations. Not sure the typical loco turnaround times would support that though...
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Come on guys: 90% 75%. The guys were on a Transatlantic heavy weight flight. Let's have apples & apples. A regular 4 hr full line flight -800 is in that ball park. Maybe I should have said 85% as a gut limit; but let's not get into a........about how low you can go. Irrelevant.
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If the system says 75%, 90% or whatever it decides is best for runway length/weight/power etc, is this the figure always put in and used for take-off, or is it possible to add an additional figure as a bit of a safeguard (similar to approach/landing at Vref +5kts). As a paying piece of SLF, I'd be more comfortable knowing that the power used is slightly more than actually required to get us off the ground safely, rather than it just being sufficient?
So will you stay at home if your next departure is one where all of the available power is needed to do a "legal" takeoff?
The point is, those legal requirements already have some safety margin built into them. Also, the settings for most reduced thrust takeoffs are calculated using an assumed temperature. So for example, if the thrust selected is for an assumed temperature of 40 C and the actual temperature is 15 C, the calculation assumes the engines will produce the amount of thrust that can be made on a 40 C day. In reality, they will produce more thrust because the actual temperature is cooler - adding even more buffer to the safety margin.
The point is, those legal requirements already have some safety margin built into them. Also, the settings for most reduced thrust takeoffs are calculated using an assumed temperature. So for example, if the thrust selected is for an assumed temperature of 40 C and the actual temperature is 15 C, the calculation assumes the engines will produce the amount of thrust that can be made on a 40 C day. In reality, they will produce more thrust because the actual temperature is cooler - adding even more buffer to the safety margin.
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RetiredBA/BY
It should be easier to implement these days.
In fact, I think a smartphone app would be quite possible for many phones that have good accelerometer sensors.
You only need 3 parameters. Takeoff length, end speed, and a start time/button. Length determines average G's needed over a certain time period. If too much of a deficit is accumulated by a predetermined time on the way to V2, then an alert is issued.
To whomever decides to make this app... I'll PM you my bank info for my 10% royalty cut.
It should be easier to implement these days.
In fact, I think a smartphone app would be quite possible for many phones that have good accelerometer sensors.
You only need 3 parameters. Takeoff length, end speed, and a start time/button. Length determines average G's needed over a certain time period. If too much of a deficit is accumulated by a predetermined time on the way to V2, then an alert is issued.
To whomever decides to make this app... I'll PM you my bank info for my 10% royalty cut.
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One of the issues identified with the of the EK521 DXB accident preliminary report was the automated RAAS system alerting the crew to a long landing. There was sufficient runway remaining for a safe stop in the remaining distance. Was this automated callout a prompt for the PF to initiate a go-around where ordinarily he wouldn't?
Automated warnings or alerts may well add new risk to the system in unintended or unanticipated ways, whilst reducing risk as intended. Not disregarding the idea, however, there are significant human factors with cognition and confusion.
Automated warnings or alerts may well add new risk to the system in unintended or unanticipated ways, whilst reducing risk as intended. Not disregarding the idea, however, there are significant human factors with cognition and confusion.
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Falcons have had a takeoff acceleration display on the PFD for years. Part of the initial takeoff PM duties is checking it against the precomputed figure. Except that this figure comes from the same EFB app as the rest of the data, so if you've input the wrong figures it won't help you.
