When I taught King Air ground school at Beech Aircraft Corporation back in the 1970s a name we used often was “lever lock switch.” In preparation for this article, I went to my dictionary to see if this word actually existed and was not too surprised to find that it did not. Instead, what I found was “toggle switch” and “locking lever.” The definition of toggle switch found is: “An electric switch with a spring to open or close the circuit when a projecting lever is pushed through a small arc.” The “locking lever” addition means that the lever cannot be moved until it is unlocked and this means that it must be pulled before it can be moved up or down or left or right. For the purposes of this article I think I will revert to the old familiar “lever lock switch” that I presume is familiar to most of my readers.
Perhaps the most common example of this type of switch in almost all King Airs is the left or right bleed air switch. If the copilot were to brush his hand against this switch accidentally as he reached for an iPad, there’d be no chance for a sudden loss of bleed air since no matter how hard he hit the switch it would not move if he had not first pulled it toward him, typically using the combination of his or her forefinger and thumb.
As years have passed, more lever lock switches appeared in King Air cockpits. The first three 90-models – 65-90, A90, and B90 – had none. Bleed air lever lock switches made their appearance on the 100 model when it premiered in 1969. But not until the appearance of the 200 model in 1974 did more lever lock switches join the cockpit controls. There is an interesting story about what prompted the appearance of two of them: the left and right “ignition” and “engine start” switches.
As you likely know, the model 200 incorporated many, many changes and improvements over its predecessors. One of these changes was the relocation of the parking brake’s control knob from its previous spot (the highest left corner of the pilot’s left subpanel) to the new one that was now the farthest left portion just below the left subpanel, where the pilot’s air valve knob previously resided. Not too surprisingly, some 200s in the first few years blew all four tires on landing. It was obvious to see why: The pilot thought he was shutting off the conditioned air flowing down toward his feet but what he actually accomplished was pulling on the parking brake: mistake!
Another change was relocating the pilot’s air valve knob to the left and slightly below where the pilot’s control wheel’s shaft exits from the subpanel and also changing how the knob functioned. Now the air flowing towards the pilot’s feet turned “on” when the valve was pulled and was shut “off” when pushed … a much more logical choice, in my opinion, than the original “backwards” design.
While the pilot’s left subpanel was undergoing these changes, why not throw in a few more? First, the designers needed to add switches for the ice vanes. Previously, they were moved solely by mechanical push-pull T-handles centered beneath the pilot’s subpanel. But now the primary actuation method was via an electric motor and the T-handles reverted to a back-up system only used if the primary system malfunctioned. The other switches on the pilot’s left subpanel got slightly rearranged and one of these changes saw the ignition and engine start switches being moved down close to the very bottom edge of the panel.
Bud Francis, the 200’s lead test pilot head, was a rather tall gentleman and one time his left knee accidently pushed both left and right start switches up to the “ignition” and “start” position as he adjusted his seat. When the battery switch came on, all onboard were quite surprised when both engines began turning! Oops!
The outcome of this incident was what we now see in almost all King Airs: The upward travel of the “ignition” and “engine start” switch is the lever lock type. It must be pulled before it can be moved up … impossible for a knee alone to do so!
To make it easy to pull, all lever lock switches in King Airs contain an obvious “blob” on the end of the lever that the thumb and forefinger can easily grasp. This blob or bulge makes the switches that require the pull, easy to recognize.
The bottom portion of this same, three-position switch – Ignition and Engine Start at the top, Off in the center and Starter Only at the bottom – does not require a pull. It does not have the locking action. From the bottom position it will spring back to the center position when released. Typically this switch would never be used in the bottom position for more than 30 seconds during an engine clearing procedure following a no light off scenario so it would be easy to keep pressing it down for that short length of time.
Quiz time: What other cockpit switch is the lever lock type – with the blob on the end of the lever – but only needs to be unlocked to move in the up or down position, not for both?
The answer: windshield heat. I will wager that over 50% of King Air pilots don’t know this unusual fact. Back in the pre-C90A days – before 1984 – only the 200-series and the 300-series had separate switches for pilot and copilot windshield heat. The other models, instead, used only one switch and one windshield temperature regulation system to control both sides. Also, the heating element was a horizontal portion that covered only about one-third of the windshield, starting downward from near the center.
There were no “Normal” or “High” heat choices like the newer models have. The switch, however, still had three positions: “Both” at the top, “Off” in the center and “Pilot Only” at the bottom. This was a simple, three-position toggle with no locking action, no need to pull. About the only time the “Pilot Only” bottom position would be used was in the event of a generator failure.
The newer windshields very seldom require the use of high heat. Keep in mind – as you pilots of these models should already know – the windshield temperature that the thermostat circuit is trying to maintain does not increase when “High” is selected. Instead, the heat is concentrated in a smaller area. The innermost five inches or so of both windshields, closest to the center post, receive no heat so that the available energy is concentrated more directly in each pilot’s line-of-sight.
The only time either the pilot or copilot windshield heat switch must be pulled is to move it to the seldom-used high heat position! Stop pulling that switch every time you grasp it! There’s no need to do that! By doing so, you make it much more likely that you will accidentally move it down to the “High” position when you meant to just turn the “Normal” heat off. Use only your index finger on that switch and reserve the thumb/index combination for the rare times you truly want high heat. Realize that if high heat is accidentally on during engine starting, the chance of blowing a current limiter in a model 200 is greatly increased.
Another switch that started as a simple toggle but then became a lever lock in later years is the inverter selector switch. (Which now has been removed as the new airplanes no longer require alternating current.) This switch, again on the pilot’s left subpanel, has always been located next to the “Avionics Master” switch and the inverter switch, before it was changed to the lever lock type and had the exact same appearance as the avionics master switch … a simple toggle. I have watched many a trainee deal with the failure of the No. 1 inverter I gave them by turning off the avionics! Oops! They hastily grabbed the wrong switch! Changing to the lever lock type makes this error highly unlikely.
The optional brake deice system’s control switch is also a standard, two-position lever lock type that must be pulled to activate or deactivate. Although located on the pilot’s right subpanel along with eight or so other anti-ice and de-ice switches, the chance of activating it unintentionally while turning on the other items is nearly impossible.
The most important takeaway from this article? Stop pulling the windshield heat switches … except when you actually want to select high heat!