456
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Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 9:56 am

Hi all - I just was wondering last night why are there still levers for the gear and flaps in the cockpit?
As cockpits have changed rapidly over the years (glass cockpit/fly by wire), they still have the mechanical large knobs for (at least) these 2 functionalities (however I assume that behind that lever there will be an electronical circuit which will lower the flaps/gear).

Why arent the flaps and gear also not used by a single (electrical) button?
 
xjramper
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:07 am

It's a human factor thing. It's a matter of repetitiveness that is both a memorized visualization and feel. You have random buttons and circuit breakers that serve their function and purpose, but nothing compares to being able to slow the aircraft down and being able to land more than those two functions. Their size has decreased over the years, but it's still the same thing. I agree that they have the technology to make them just buttons, but they see and feel it, they are less likely to forget to drop the flaps and gear.
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MD11Engineer
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:07 am

Mainly because you can feel the shape of the levers even in darkness and don´t have to start looking for a button.
You will notice that the gear lever has a head, which looks like a wheel. The flap lever on the other hand looks like an airfoil. The speed brake lever is usually straight, while the throttle levers are round, the mixture levers (on piston aircraft) are spiky and the propellor speed lever is square. The landing light switches also have a typical shape.
You can all feel these shapes without looking at them.

Jan
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PH-BFA
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:08 am

Quoting 456 (Thread starter):
Why arent the flaps and gear also not used by a single (electrical) button?

They were originally designed in such a manner that they could be easily found if, for example, the cockpit would be covered in smoke; the gear lever therefore resembles a 'wheel' and the traditional boeing flap lever resembles a 'flap'.
 
Bongodog1964
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:11 am

In an emergency a big lever will always beat some pretty buttons, to my mind its instinctive to a pilot in trouble, gear up - throttles to max, plus of course the levers have a detent, so you have to consciously lift the lever and push/pull. Introduce some buttons and in an emergency someone might press the wrong ones.
 
456
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:26 am

Thanks all - That sounds quite logical indeed.
I can imagine that during an emergency where there is less visibility, the levers can 'always' be found.

Furthermore - it shows you immediately the exact status of the lever during the landing/start procedure, minimizing mistake or misreading.

Never thought about that.

Thanks!
Marc
 
sandyb123
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:39 am

Quoting MD11Engineer (Reply 2):
You will notice that the gear lever has a head, which looks like a wheel. The flap lever on the other hand looks like an airfoil. The speed brake lever is usually straight, while the throttle levers are round, the mixture levers (on piston aircraft) are spiky and the propellor speed lever is square. The landing light switches also have a typical shape.
You can all feel these shapes without looking at them.

Seems to make sense. Are these various levers just connected to the FMC / computers which in turn controls these mechanical functions or are they 'physically' controlling the equipment?

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Dalmd88
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 10:44 am

In many airliners those levers are moving little electrical switches or resolvers that send a signal to the component or a computer to move. So we have come a long way from a bunch of levers moving cables.
 
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garpd
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 1:02 pm

IMO, it's all bout know what is where without having to rely on a readout.

A Pilot knows what position the flaps should be at with a cursory glance at the lever.
Same for the throttles. The same can be said for the yoke also, which is one reason why Boeing continue to use it; It gives a pilot instant identification of what commands the person next to them is inputting, even in pitch darkness or smoke.
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tdscanuck
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 1:14 pm

Quoting 456 (Thread starter):
Why arent the flaps and gear also not used by a single (electrical) button?

Out of curiosity, how would you do flaps with a single button? I can see how you'd do it for gear, but for flaps I think you'd need at least two (one for up, one for down) although that would be a human factors nightmare.

Quoting sandyb123 (Reply 6):
Are these various levers just connected to the FMC / computers which in turn controls these mechanical functions or are they 'physically' controlling the equipment?

No aircraft I'm aware of has them tied into the FMC. In many current designs the levers are actuating microswitches that directly command the equipment, or directly command the boxes controlling the equipment. In FBW designs, especially with the flaps, you may just have a resolver that's sending a position signal to the flight control computers, which then do whatever they need to do. Landing gear has lagged behind flap control in terms of sophistication because it is, comparatively, such an easy function (up or down), and a stuck flaps landing is more pleasant than a stuck gear landing.

Tom.
 
RebelDJ
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 1:28 pm

Quoting 456 (Thread starter):
Why arent the flaps and gear also not used by a single (electrical) button?

One of the reasons would be that certain controls are required to have certain shapes - see regulation CS25.781 or FAR 25.781.
 
DualQual
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RE: Why Are There Still Levers In The Cockpit

Tue Dec 18, 2012 1:36 pm

Boeing flap levers also have gates on them to force you to stop the handle at the go around flap position in the event of a go around from the landing flap setting.
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CaptCufflinks
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RE: Why Are There Still Levers In The Cockpit

Wed Dec 19, 2012 12:55 am

Quoting sandyb123 (Reply 6):
Seems to make sense. Are these various levers just connected to the FMC / computers which in turn controls these mechanical functions or are they 'physically' controlling the equipment?

I can't think of any aircraft where the FMC can dirty or clean the aircraft.

A lot of modern airliners, however, have flight management computers and systems that adjust their VNAV and performance readings depending on the configuration of the aircraft. The Pegaus FMC system used on some Boeing aircraft, for instance, can inform a pilot that 'drag required', meaning some form of manual input is required to attain a certain descent profile - it's not automated.
 
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Starlionblue
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RE: Why Are There Still Levers In The Cockpit

Wed Dec 19, 2012 2:19 am

In some ways, nothing is more dangerous than flaps and gear. You DO NOT want to screw them up. Very very basic airmanship but things happen fast up there. It all seems simple "in theory" but once you're up there it is amazing how you can get distracted and overworked.

Please don't make flaps and gear a touchscreen button.

Check this out. The sound you hear is, you guessed it, the gear warning horn... http://www.youtube.com/watch?v=-K4QHpVXtxI. How could they miss it? They didn't do their GUMPS check...
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Woodreau
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RE: Why Are There Still Levers In The Cockpit

Thu Dec 20, 2012 3:07 am

One flight deck that is pretty dangerous (in my mind) is an embraer flight deck - every switch in the upper overhead feels exactly the same. The switches that controls whether the engine is running or not feels exactly the same as the ignition switches and APU and fuel pump and hydraulic switches.

It was so bad they had to install guards over the engine switches to keep a pilot that is reaching up for say the ignition switches from accidentally switching off the engines inflight. With the e170s/190s, the engine switches still feel exactly the same as all the other switches but they moved them from the overhead panel to the center pedestal.
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Kaiarahi
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RE: Why Are There Still Levers In The Cockpit

Thu Dec 20, 2012 8:39 pm

Quoting tdscanuck (Reply 9):
for flaps I think you'd need at least two (one for up, one for down) although that would be a human factors nightmare

Many Cessna models had self-centering switches. Variations included hold for extend, one touch retract.
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Jetlagged
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RE: Why Are There Still Levers In The Cockpit

Sat Dec 22, 2012 1:29 am

Quoting DualQual (Reply 11):
Boeing flap levers also have gates on them to force you to stop the handle at the go around flap position in the event of a go around from the landing flap setting.

Airbus flap levers are exactly the same, for the same reason, but the gate mechanism is internal to the lever unit, not an external mechanical gate, as with Boeing.
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