This is a question I’ve published in the past, but is a good one to repeat for those who may not have owned a King Air when it was published earlier.
I was looking through some BE-200 landing gear information and wondered about the following:
For 200s and B200s with the electro-mechanical gear, the checklist says that airspeed should be below 130 knots and states, “Do Not Stow the emergency gear extension handle after you have pumped the gear down sufficiently to get all three green lights.”
For the B200s with the later hydraulic gear, the checklist makes no mention of slowing down first and specifically states that if all three green down lights are illuminated to go ahead and “Stow the emergency gear extension handle.”
Would you please clarify why there is a difference? If you have any other comments on peculiarities and other differences in these landing gear systems, feel free to throw them in too!
I personally do not believe the 130 KIAS figure is very important but, by being at a slower speed, the initial opening of the nose gear doors is a little easier, since their leading edges tuck a bit into the air flowing past the nose. In the hydraulic system, those first pumps merely remove the pressure that is holding the gear up and gravity will now take over and do much of the rest. Since the relative wind helps the mains extend but hinders the nose, the mains fall to what appears to be fully extended – but they’re not locked – whereas the nose ends up at about a 45-degree angle. So it still takes close to 100 pumps on the red handle (even more than those needed in the mechanical system!) to finally get all three green lights to come on as the locking takes place.
There is so much mechanical advantage designed into the manual ratchet device associated with the electro-mechanical system that pumping it past the point of the gear being fully down and locked could lead to damage … probably bending an actuator rod or nose gear brace since there is no more room for further travel of the gear. Since taking even an extra half-stroke or so to stow the handle could cause damage, it’s not advisable. After all, the mechanic is going to have to jack the plane and see what’s wrong anyway, right?
The main reason for stowing the handle in the hydraulic system is that when the handle is down to floor level, it relieves the pressure in the emergency extension lines. Once the green lights come on, indicating the gear is mechanically locked in the fully down position, there is no reason to maintain the pressure there, so relieving it (1) leads to less chance of a leak developing, and (2) makes it possible for the gear to be retracted normally. (That is especially important if this was an in-flight emergency extension conducted for training purposes.) If the pressure is not relieved before the CB is reset and the gear handle is raised, often the motor will run in excess of the 14 seconds or so that triggers the automatic shutdown, including the blowing of the Landing Gear Relay circuit breaker.
You didn’t mention it, but I am sure you know the checklist for the procedure relating to the hydraulic system also specifically states to not stow the handle and, in fact, to keep pumping it often until jacks are under the jack points, if a green light will not illuminate. The thinking here is that even if the gear actuator wasn’t moving all the way to cause the lock to function, missing it by just a bit, sufficient pressure kept in the emergency extension lines may keep the gear extended until the maintenance folks get the jacks positioned.
One last comment: If you are doing a landing gear manual extension exercise for training purposes in the electro-mechanical system – either during a training flight or while the airplane is supported on jacks for routine maintenance – sometimes you may run into a little snag when the procedure is finished and the three green lights are on. Since the procedure directed you to not stow the handle, now what? The Beech Abnormal Procedures checklist specifically includes a procedure for getting things back to normal after a practice manual extension … since, of course, at some time the handle has to be stowed to return to normal.
This extra procedure directs you to rotate the C-ring counterclockwise and let it return down to floor level. What this should do is release the manual system and allow the motor to again take control. The little snag is that, sometimes, it binds up and does not release. How do we know? Because the ratchet handle is still stiff and hard to move. Remember that we’re not supposed to pump any more, due to the probability of damaging something, so stroking the handle again in hopes of releasing the binding is not a good idea.
Here’s the technique that almost always works: Place the gear handle in the up position. (You will have to use the downlock release button since with the landing gear relay circuit breaker (CB) that pulled the handle’s downlock hook remains engaged.) Now, “bump” the CB. What this means is to grasp the CB firmly between thumb and finger, push it in only until you hear the motor start to run, then immediately pull it out again. In other words, we give just a little bump to the motor. Invariably, this trick frees up what was binding the manual extension handle. Make sure the handle moves freely – which I am sure it will – and go ahead and stow it in the retaining clip. Depending upon where you want the gear to be, either verify your airspeed is below gear retraction speed, push the relay breaker in, and watch the gear retract normally. Or leave the handle down, reset the breaker (the motor will probably run for just a fraction of a second) and verify normal gear down indications.
Thanks for the good question. I welcome readers to ask about anything at all, King Air related, and I hope I can provide a clarifying answer.
