Cockpit engine and system controls, switches
Thread Starter
Fleet Manager
Joined: Aug 2006
Aviation Qualifications: CPL
Posts: 7,081
Likes: 2,938
From: Ontario, Canada
As a pilot, while flying, I will want to the airplane to do something. It will be in my mind what that something is, all that remains, is "how do I make the plane [systems] do this? 99% of the time, my training, and experience will have me know what control/switch/etc. I will need to move, and how. Therefore, I'll be seeking out the switch with that function. 1% of the time, it's confusing. If confusing, I will reconsider the nomenclature of the switch, look for placards, and read the flight manual. Nearly always, the combination of "what do I want the airplane to do?" combined with my understanding of what I understand the switches (and other controls) do will get me where I want to be.
The airplane designers, and certifiers (what I do for a living) are responsible to design and identify controls, and provide adequate placarding, and flight manual information so the pilot can clearly understand how to use a control (switch) what it does, and any cautions. Two examples of undesirable come to my mind:
While delivering a GA airplane years ago, I had filled the auxiliary fuel tanks for the long flight. Though I had lots of experience with this airplane type, I had never before flown one with the optional auxiliary fuel tanks. Along the way, I decided it was time to start to use that fuel, to assure that my main tank (there is only one, on this type) would be well up for landing. I could not find whatever control would be used to move fuel from the auxiliary fuel tanks to the main tank. I had time, so I read every placard in the cockpit, I read the flight manual, I even read the placards at the fuel fillers, which i could see from the cockpit - zore information on how to transfer fuel. So, I phoned the boss, to ask. He told me that the auxiliary fuel would automatically drain into the main tank to keep it well filled, no pilot action required. Wow, simple system - okay. But, a placarding error in the design, a cockpit placard near the fuel quantity indicator should be placed to tell me that!
Example two: While ground running a prototype airplane with a very new engine installation, As a part of a (yet to be defined) preflight, runup check, I operated a pilot "FADEC Test Switch". I had operated similar switches on similar FADEC controlled engines, and the check was benign. Not this one! The engine went to 80% power with the operation of the switch. Fortunately, I was chocked on the apron, so the airplane did not b=move, but I held the plane hard while it ran this test. I just held in and waited - the test ended. What I did not know, and was not placarded, was that by touching the power lever during the test, it would abort. 'Wish I'd known that! So, as I will be the lead on certifying that system, I have strongly suggested that that switch be moved away from the pilot, and guarded, so as to be a "maintenance only" operation switch. The pilot would be able to access it to perform the test, but under direction from maintenance people, it will no longer be a pilot preflight check. This, in particular, because this airplane could be configured as a floatplane, in which case this power setting would probably get the plane airborne!
In any case, a switch, or other control, is there so the pilot can use it to fulfill his/her intent that the airplane do the desired next thing. The switch is the path to complete the pilot's intentions. The precise function of operation of the switch itself might need a bit of understanding (lift toggle to move), but otherwise should be simple and common to the pilot's expectations.
The airplane designers, and certifiers (what I do for a living) are responsible to design and identify controls, and provide adequate placarding, and flight manual information so the pilot can clearly understand how to use a control (switch) what it does, and any cautions. Two examples of undesirable come to my mind:
While delivering a GA airplane years ago, I had filled the auxiliary fuel tanks for the long flight. Though I had lots of experience with this airplane type, I had never before flown one with the optional auxiliary fuel tanks. Along the way, I decided it was time to start to use that fuel, to assure that my main tank (there is only one, on this type) would be well up for landing. I could not find whatever control would be used to move fuel from the auxiliary fuel tanks to the main tank. I had time, so I read every placard in the cockpit, I read the flight manual, I even read the placards at the fuel fillers, which i could see from the cockpit - zore information on how to transfer fuel. So, I phoned the boss, to ask. He told me that the auxiliary fuel would automatically drain into the main tank to keep it well filled, no pilot action required. Wow, simple system - okay. But, a placarding error in the design, a cockpit placard near the fuel quantity indicator should be placed to tell me that!
Example two: While ground running a prototype airplane with a very new engine installation, As a part of a (yet to be defined) preflight, runup check, I operated a pilot "FADEC Test Switch". I had operated similar switches on similar FADEC controlled engines, and the check was benign. Not this one! The engine went to 80% power with the operation of the switch. Fortunately, I was chocked on the apron, so the airplane did not b=move, but I held the plane hard while it ran this test. I just held in and waited - the test ended. What I did not know, and was not placarded, was that by touching the power lever during the test, it would abort. 'Wish I'd known that! So, as I will be the lead on certifying that system, I have strongly suggested that that switch be moved away from the pilot, and guarded, so as to be a "maintenance only" operation switch. The pilot would be able to access it to perform the test, but under direction from maintenance people, it will no longer be a pilot preflight check. This, in particular, because this airplane could be configured as a floatplane, in which case this power setting would probably get the plane airborne!
In any case, a switch, or other control, is there so the pilot can use it to fulfill his/her intent that the airplane do the desired next thing. The switch is the path to complete the pilot's intentions. The precise function of operation of the switch itself might need a bit of understanding (lift toggle to move), but otherwise should be simple and common to the pilot's expectations.
