Yes, that is a long title. If you fly a King Air with the electrohydraulic landing gear system, this article is not for you. But if you are flying a C90-1 or earlier member of the 90-series, an E90, most F90s, any member of the 100-series (straight 100, A100 or B100) or a 200 built before the 1985 model year, then there is worthwhile information in this article for you.
The main landing gear got heavier when dual main wheels, tires and brakes appeared with the introduction of the model 100 in 1969, replacing the single wheel, tire and brake used on the 90-series. This system, designed to carry heavier loads, originated in the Beechcraft Model 99 “Airliner” that went into production a year earlier, in 1968. With minor changes, the 99’s landing gear system was incorporated into the King Air 100. This is the system that then became standard in all versions of the 100-series, all members of the F90 family (except for the last 11 serial numbers, LA-226 through LA-236), and slightly more than the first 1,100 200s and B200s, up until 1985.
This larger, heavier main gear system required a bigger electric motor to allow for retraction and extension in similar times as had been the norm in the 90-series. The larger motor, in turn, required heavier wiring and the 50-amp circuit breaker on the aft end of the pedestal was replaced with a 150-amp current limiter under the floor.
Operationally, however, the pilot found the systems on the single-tire and double-tire gear systems identical, except for small changes in gear limit speeds. Gear down and up indications, the landing gear warning horn’s functionality, even the emergency extension procedures all remained the same … or so it seemed to the pilot.
But, under the floor, there is a big difference when it comes to manual extension. The “Emergency Engage” red-painted C-ring between the pilot’s seat and the pedestal is the same on all of these models. After (1) slowing down to the proper speed per the checklist procedure, (2) pulling the landing gear relay circuit breaker (on the instrument subpanel, right beside the landing gear handle), the third step is to pull up the C-ring as far as it will travel – about 2 inches – and twist it clockwise as far as it will go – about 60 degrees – to lock it in the “up” position.
The most significant result of pulling the C-ring up is that the chain that the ratchet handle drives has now been engaged into the landing gear transmission, or gearbox. Realize that the only malfunction that can be cured by using landing gear manual extension is failure of the motor. The pilot’s muscle power can be substituted for the motor’s power. That’s it; nothing else. Jammed jackscrew? You’re out of luck. Broken main gear drive torque tube? Out of luck. Nose gear chain jammed on a sprocket? Out of luck.
The landing gear system’s reliability is not a King Air weakness. Rarely does the crew need to use the manual extension procedure. When they do, the outcome is almost always successful … but not always.
Suppose that the motor itself jams, becomes unable to turn. There is a second event that takes place when the C-ring is pulled, in addition to engaging the ratchet handle into the transmission. This event, however, is totally different in the single-main-tire versus the dual-main-tire airplanes.
In the LJ- and LW-series – 90, A90, B90, C90 and E90 – the motor gets disconnected from the transmission. How cool is that?! So, in the unlikely event that the reason for manual gear extension was that the motor’s armature could not turn – bad bearing, binding on its housing – no problem! Once the C-ring has been pulled, say “bye-bye” to the motor. It is physically removed from the gearbox, the transmission. Hence, the manual ratchet can rotate the transmission and drive the left and right main actuator torque tubes and the nose gear chain just fine.
But that’s not so in the F90-, 100- and early 200-series. In those airplanes, a motor’s armature that cannot rotate means that manual landing gear extension is impossible. I certainly was not on the 99’s landing gear design team and therefore am not privy to the exact reasons why the change was made. With the bigger motor, however, pulling of the C-ring does not disengage the motor from the transmission. Engage the manual ratchet drive? Of course. Disengage the motor? No.
Here’s a little “war story” I heard a long time ago involving an early model 200 based in Anchorage, Alaska. Departing without passengers on a positioning flight, the gear failed to completely retract. Realizing the situation, the crew decided to remain in the Anchorage area to pump the gear down manually and return to home base. Uh-oh! The ratchet handle wouldn’t move!
Both pilots were also A&P mechanics, they had a good supply of tools on board, and had over four hours of fuel in the tanks. Relaying through their dispatch operation they talked to the Beechcraft factory customer service department and found that the only solution would be to disconnect the motor from the transmission. No sweat! They had the qualified manpower, plenty of time and the proper tools … so they thought.
As one pilot continued to fly in a wide pattern around the airport, the other fellow got out of his seat, rolled back the carpet, removed the appropriate floor access panel, found the motor and proceeded to start undoing the four bolts that connect the motor to the transmission. Unfortunately, he found that he could not remove the fourth bolt. Its nut was in a position that required a specially bent wrench to hold it from turning.
Hours went by in fruitless attempts to remedy the problem. As the sun was getting low – relatively early in the afternoon during the Alaskan winter – the decision was made to land before it got too dark. I was told that a common Anchorage procedure for a gear-up landing in those bygone years was to plow snow back onto the runway instead of using foam. This was done, the 200 landed with relatively minor damage, and was back in service within a few weeks.
Since the motor is still connected to the landing gear transmission in the dual-mains models, it would be bad for the landing gear motor to start running after the C-ring has been pulled. The ratchet handle would be a blur as it rapidly got pulled along with the transmission to which it was now connected. Thus, there is a second thing that the C-ring does besides engaging the ratchet but it is not the same as in the LJ- and LW-series: It opens the electrical control circuit to the “up” side of the motor.
Now remember, the control circuit breaker (CB) should be pulled before the ratchet is engaged by pulling up the C-ring. With the CB pulled, no power can get to the motor, period! Nevertheless, if some careless pilot overlooked the checklist procedure and failed to pull the CB, at least the motor could not start running the gear up while he or she was trying to pump it down!
To recap: Pulling the C-ring does two things in all cases. First, it engages the sprocket driven by the manual ratchet handle into the landing gear’s transmission, allowing the pilot’s muscle power to replace the electric motor’s power. Second, for the LJ- and LW-series, it physically disconnects the motor from the transmission. Second, for the LA-, B-, BE- and BB-series, it opens the UP electrical control circuit.
A final comment or two: After a manual landing gear extension has been performed either as a training exercise or during a maintenance inspection, be aware that there are a couple of “tricks of the trade” to ensure that all will be well when the system is returned to normal operation. In the 90-series, there is a definite chance that the driving gear from the motor may no longer be aligned with the driven gear in the transmission. If the motor now begins to operate to start gear retraction, there is a chance the gear teeth will take a beating until proper alignment occurs as the driving and driven gears finally mesh. The solution? Don’t push the control CB in once the landing gear handle is in the up position asking for normal retraction. Instead, “bump” the circuit breaker a couple of times first. “Bump,” in this context, means to grasp the CB by its sides with thumb and finger and push it in just far enough to make brief electrical contact, to hear the motor start to run, then pull it again. If the gears happened to have already meshed perfectly, this doesn’t hurt a thing. But if by chance the gears had not yet properly meshed, the minor rotation of the driving gear will ensure that the driven gear has been properly mated.
Since the motor is never disconnected in the dual-tire series, there is no worry about the gears not being aligned. Instead, the problem is that sometimes the gear won’t retract when the CB is pushed back in! This is because the switch that disconnected the up circuit may have stuck in the activated position. Before rolling back the carpet and getting the tools, just pull the C-ring back up and let it fall freely back down to floor level. There’s a spring pulling it down, so it usually snaps back to floor level quite aggressively. Doing this once or twice almost always frees the sticky switch and now the gear will retract properly.
May all your landings be with all three gear legs down and locked, no matter how they got there!
King Air expert Tom Clements has been flying and instructing in King Airs for over 46 years and is the author of “The King Air Book” and “The King Air Book II.” He is a Gold Seal CFI and has over 23,000 total hours with more than 15,000 in King Airs. For information on ordering his books, contact Tom direct at twcaz@msn.com. Tom is actively mentoring the instructors at King Air Academy in Phoenix.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at editor@blonigen.net.