Vmid a new call-out speed on TO and Landings

[TRISTAR1]

VMID

I started to develop a monitor in conjunction with Dan Air in the early 80's. We actualy filled a patent application.

During discussions with the then ARB it was pointed out that this equipment would increase the number of rejected take offs by a factor of 10. This would then cause accidents that would not have happened if the aircraft had gone instead of stopping.

Dead duck I'm afraid

[wileydog3]

Originally Posted by jondc9

but the $ or the POUND STERLING or whatever seems to bother us all.


a good idea worth expanding on...but $ and idiots in the FAA and others such places along with backward thinking management will doom this idea(though I hope not)

j

Another 'gizmo' in the cockpit is not necessarily needed. Before retiring, I began
hacking the clock and noting time to 80kts. I also began tracking my speed at 1000ft and at 2000ft. With max power or derates or assumed temps, the timing came out about the same (assuming the data was based on a given and you used that thrust ie.. it called for derate and you used it and not max thrust).

No runway markers? Well, take out the airport diagram and half the runway. Do it again. If needed, do it again. You will be able to see that taxiway x is right about 2000ft or that a feature is near 1000ft.. or use the marking on the runway.

By paying attention to the routine, you begin to learn what is routine and what is not. You learn early on when the machine or the environment is not what you expected or planned for and you have time to do something about it.

The call for more gizmoes only reminds me of Weiner's Law (or one of them) and that is for every new technology introduced, a new error is introduced. Before retractable landing gear, gear up landings were not a problem...

[FullWings]

The call for more gizmoes only reminds me of Weiner's Law (or one of them) and that is for every new technology introduced, a new error is introduced.

We have this 'gizmo' called GPWS. I'm too young to remember life before its introduction but I'm sure some at the time regarded it as an affront to their piloting skills to have such a device fitted. I understand the first few iterations of the equipment were more prone to false warnings but that has been sorted and we all accept it as a life-saver now.

I started to develop a monitor in conjunction with Dan Air in the early 80's. We actualy filled a patent application... ...Dead duck I'm afraid

Twenty+ years ago we didn't have access to the precision position measurement technology and signal processing power that we do today - maybe it's time to revisit this area?

[wileydog3]

Originally Posted by FullWings

We have this 'gizmo' called GPWS. I'm too young to remember life before its introduction but I'm sure some at the time regarded it as an affront to their piloting skills to have such a device fitted. I understand the first few iterations of the equipment were more prone to false warnings but that has been sorted and we all accept it as a life-saver now.
Twenty+ years ago we didn't have access to the precision position measurement technology and signal processing power that we do today - maybe it's time to revisit this area?

I spoke with a couple of engineers and pilots a few years ago about 'mode proliferation' and 'mode confusion'. They were with a big airplane company. They explained that one problem they had was what to include and what to exclude. yes, they could design a system to do 'x' but they often wondered why and if they included every 'gizmo' that the pilots wanted, the cockpit would have thousands of gizmoes. And there would not be enough time to train on what they did or as importantly, failure modes.

I have had a chance to fly some new generation GenAv airplanes and I have seen guys so fascinated with the displays they seldom look at huge display called a 'window' (technical term). yes, there is a place for new technology and there is a place for new 'gizmoes' but that does not negate Weiner's Law about inducing a new error potential.

Do you know the average fuel burn for your airplane for the first, second and third hour? Do you know how to quickly calculate a no-wind ISA altitude for a leg and basically how long it will take block to block?

I still think the greatest device in the cockpit is a well trained, attentive, proficient pilot...

[FullWings]

Originally Posted by wileydog3

I still think the greatest device in the cockpit is a well trained, attentive, proficient pilot...

Agreed but however well-trained you are or how proficient you think you might be, it is difficult/impossible for a human being to be 100% attentive all the time.

If a gizmo is fitted to your aircraft that stays silent for 10,000 sectors then produces a genuine warning that you are attempting to take off on the wrong runway (at night, in the rain/mist, after a long day, etc.) then how much is that worth to you? Or the people sitting behind you?

Something like a TPM doesn't have to be a 'flash' piece of techno-wizardry. It doesn't need any interface at all, really: just to work when it's needed and to be an invisible part of the aircraft systems when it isn't.

[qwertyuiop]

There has been a gizmo available for years, its called a compass. Set it to the runway hdg before taxi and then check before t/o. You could then include in pre T/O checks. Simple!

[Mad (Flt) Scientist]

Originally Posted by TRISTAR1

During discussions with the then ARB it was pointed out that this equipment would increase the number of rejected take offs by a factor of 10. This would then cause accidents that would not have happened if the aircraft had gone instead of stopping.
Dead duck I'm afraid

I would tend to agree; it sounds like it would be quite challenging to simultaneously detect a useful performance shortfall AND avoid numerous false warnings, ESPECIALLY given the tendency to conduct reduced tyhrust takeoffs in large numbers.

[aardvark2zz]

Originally Posted by TRISTAR1

....During discussions with the then ARB it was pointed out that this equipment would increase the number of rejected take offs by a factor of 10. This would then cause accidents that would not have happened if the aircraft had gone instead of stopping.
Dead duck I'm afraid

You have to quantify a bit more what you define as an accident during a rejected TO below Vmid.

A false-positive of a Vmid rejected TO at around 90 knots on a 10000 ft runway should not be disastrous (when below V1 and it is not an issue).

Obviously all angles have to be covered and quantified.

On another point: obviously once you reach V1 then you can drop Vmid if that is the case.

[FullWings]

Originally Posted by Mad (Flt) Scientist

I would tend to agree; it sounds like it would be quite challenging to simultaneously detect a useful performance shortfall AND avoid numerous false warnings, ESPECIALLY given the tendency to conduct reduced tyhrust takeoffs in large numbers.

Ah but it depends where you set the threshold for cautions/alerts/warnings and what you do/don't inhibit at various stages of takeoff.

I was envisaging something that (to start with) would only warn you if your projected takeoff, under current acceleration/mass/flap, etc. was going to use more runway than was available to you or that the initial climbout path would intersect with any obstacles present. This scenario is so far removed from normal all-engines operation that prediction should be much easier.

The 'MK I' of this unit could simply protect against "clear and present danger", i.e. you ARE going to CRASH if you don't DO SOMETHING NOW!

[barit1]

Vmid seems to me to have a lot of validity in that a distance-based abort (midpoint) will almost always be a relatively low-speed abort (lower than V1) and so fairly benign. Stopping with guaranteed half the runway left - Is that a BIG deal to anyone?

[TheOddOne]

The Landing case

Looking at the landing case for a moment...

We have introduced some new technology at Gatwick in the past couple of years. We have, for the 2nd & 3rd Rapid Exit Taxiways (RETs) introduced 300, 200 and 100 metre countdown lights, just to the side of the runway centreline. Admittedly we want people to use these to expedite their vacating the runway, but they are a very clear indication, both by day and night, of where you are in relation to the point at which you should be leaving the runway and planning your braking accordingly. These lights are known as RETILS and pilots have generally been positive about their introduction. Our regulator has also been very helpful, so it is possible to introduce new ideas in a reasonable timescale.

TheOddOne

[TheOddOne]

The Departure case

Again at Gatwick, I don't believe we've had a rejected takeoff anywhere near V1 in the past million or so departures (eight years), so it's in the 'remote' bracket statistically. We get quite a few at around the 60kt mark, but they're usually not much of a drama, vacate the runway, have it inspected and have another go if all indications are normal or brake temps aren't significant. This seems to me to indicate that most problems become apparent at an early stage in the t/o process, be it an engine indication anomaly or an ASI difference, config warning or whatever. Any device or procedure that MIGHT come in handy in less than a million takeoffs when other procedures seem to adequately cover the requirements does seem rather less than worthwhile.

We certainly remember the rejections close to V1 because what with the tyrebursts, wheel/brake weldings etc etc it normally closes the runway for half a day, not clever at the world's busiest single-runway airport!

Cheers,
TheOddOne

[chornedsnorkack]

Originally Posted by TheOddOne

Again at Gatwick, I don't believe we've had a rejected takeoff anywhere near V1 in the past million or so departures (eight years), so it's in the 'remote' bracket statistically. We get quite a few at around the 60kt mark, but they're usually not much of a drama, vacate the runway, have it inspected and have another go if all indications are normal or brake temps aren't significant. This seems to me to indicate that most problems become apparent at an early stage in the t/o process, be it an engine indication anomaly or an ASI difference, config warning or whatever. Any device or procedure that MIGHT come in handy in less than a million takeoffs when other procedures seem to adequately cover the requirements does seem rather less than worthwhile.
We certainly remember the rejections close to V1 because what with the tyrebursts, wheel/brake weldings etc etc it normally closes the runway for half a day, not clever at the world's busiest single-runway airport!

The scenario where the runway location could be very important is if an airplane for some reason does not gain airspeed as fast as desired, and approaches the end of runway with too low speed.

This can mean that they either reject before V1 but do not have enough available runway and overrun, or else attempt takeoff at too low airspeed and cannot stay airborne. Both very bad outcomes.

How many accidents could and should have been avoided by rejecting takeoff earlier?

[Mad (Flt) Scientist]

How is the Vmid system going to know whether the runway is dry or wet, or worse? If it needs to know whether you can stop or not this would seem to be pretty important....

[barit1]

If V1 occurs first, then Vmid isn't of any benefit.

But if midpoint distance happens first, and you haven't reach Vmid (let alone V1), then it's a lower abort speed and therefore less taxing.

[barit1]

Just a thought: if the runway changes slope at/near the midpoint, then I guess it would make sense to adjust the "midpoint" to an "effective midpoint", which might have certain assumptions or compromises in determining its exact location.

My head's starting to hurt...

[john_tullamarine]

.. ah .. now that's where a bit of math juggling comes in as the majority of standard calcs work on average slope. As blind Freddy would accept ... a marked difference (up/down) creates some calc deltas when spread across the accel and decel parts of the ASDR particularly.