David Paule
Well Known Member
When I designed the control lock for my Cessna 180, I realized that I needed to have some way to make sure than I couldn't fly the plane with it engaged. I chose this one:
I made the thing so that I can't sit on the pilot's seat with it engaged. It blocks the seat.
This works well.
Of course one reason it works well is that I never fly from the passenger side. I don't feel comfortable there and just flat won't do it. If I did once in a while, the position and design of my control lock would not be sufficient.
Today, in Aviation Week and Space Technology, there's an interesting article about a Gulfstream takeoff crash that killed several people. The two pilots started their takeoff run with the gust lock engaged. The airplane has a throttle interlock to the gust lock, preventing more than 6 of the full 40 degrees of throttle travel, but the pilots were able to defeat it by engaging the autothrottle. The gust lock remained locked.
in the article, there are two checklist items that the Gulfstream pilots neglected: one was to disengage the gust lock. The next was to do a control movement check. The pilots did neither. You might argue that failing to follow the checklist was the cause of the accident, but I'd say that allowing the autothrottle to work with the control lock engaged was certainly another; any of the three should have done the job. Also, since two of them are checklist items, if the pilots didn't bother with the checklist, they've already bypassed two of the safety measures.
One issue with the Gulfstream's control lock design is that two of the designer's ways to ensure that the locks were disengaged were of the same type, and susceptible to the same mode of failure. To use Paul Dye's term, they were similarly redundant. The throttle interlock was a dissimilar redundancy.
On our simpler airplanes, a throttle block or starter block would probably be effective. So that's a second design approach to preventing an attempted takeoff with the controls locked.
Another design approach mentioned is to connect the gust lock with the nosewheel steering so the plane can only taxi in a circle with the control lock engaged. This one might be adaptable to RVs without too much difficulty.
Dave
I made the thing so that I can't sit on the pilot's seat with it engaged. It blocks the seat.
This works well.
Of course one reason it works well is that I never fly from the passenger side. I don't feel comfortable there and just flat won't do it. If I did once in a while, the position and design of my control lock would not be sufficient.
Today, in Aviation Week and Space Technology, there's an interesting article about a Gulfstream takeoff crash that killed several people. The two pilots started their takeoff run with the gust lock engaged. The airplane has a throttle interlock to the gust lock, preventing more than 6 of the full 40 degrees of throttle travel, but the pilots were able to defeat it by engaging the autothrottle. The gust lock remained locked.
in the article, there are two checklist items that the Gulfstream pilots neglected: one was to disengage the gust lock. The next was to do a control movement check. The pilots did neither. You might argue that failing to follow the checklist was the cause of the accident, but I'd say that allowing the autothrottle to work with the control lock engaged was certainly another; any of the three should have done the job. Also, since two of them are checklist items, if the pilots didn't bother with the checklist, they've already bypassed two of the safety measures.
One issue with the Gulfstream's control lock design is that two of the designer's ways to ensure that the locks were disengaged were of the same type, and susceptible to the same mode of failure. To use Paul Dye's term, they were similarly redundant. The throttle interlock was a dissimilar redundancy.
On our simpler airplanes, a throttle block or starter block would probably be effective. So that's a second design approach to preventing an attempted takeoff with the controls locked.
Another design approach mentioned is to connect the gust lock with the nosewheel steering so the plane can only taxi in a circle with the control lock engaged. This one might be adaptable to RVs without too much difficulty.
Dave