Avidflyer2
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Piper PA34-200T - Landing Gear Up / Power Reduced Warning Switch - Alias Gear Warning Throttle Switch, PN: V3-1
Let me start off with saying unless you are involved with multi-engine training, involving single engine operations or simulated single engine operations, you'll probably never notice the landing gear warning switch's function in normal flight operations until it is too late. The switch operates the gear unsafe light and the gear warning horn whenever the landing gear is Up and one or both engines are at 14"Hg manifold pressure (idle power). The reminder to lower the landing gear may come too late in the flare during landing, at the instant when power is reduced to idle!
The problem here was that the landing gear warning horn and gear unsafe light were not working every time one or the other throttle levers were brought to idle while the landing gear was retracted. The warning switch is activated by actuator levers having phenolic blocks attached at one end to trip or operate the single switch. The V3-1 microswitch has a JV-7 Actuator Lever that is simply too narrow (.190") to reliably trip when either the left or right actuator lever's phenolic block passes beneath the switch. The two blocks (left and right) are separated by what seems to be the same or similar dimension (.180 - .190") as the width of the actuator lever on the microswitch! This is really a poor design by Piper that can be improved immensely by a wider actuator lever than the present JV-7 lever.
I had the misfortune to replace both throttle lever actuator arms (PN: 96163-00 Actuator, left & 96163-01 Actuator, right) behind the instrument panel in a most inaccessible location as what can be imagined, only to find that the new actuator arms did not correct the too-wide spacing problem between the two actuator arms. A new microswitch actuating lever JV-7 did not correct the problem either as the replacement was the same width as the previous lever.
I then tried installing two microswitches, each with their own actuating lever JV-7 and had problems with both microswitches operating at different set points. This entailed spacing the switch bracket outboard and away from the left side mounting bracket about .090" so that the centerline of the two switches was centered between the two throttle lever actuating arms.
Hmm, unable to locate a wider actuator lever for the microswitch... two microswitches operate at different times... what about two microswitches operated by a single wider actuator lever made for two switches mounted in tandem? Eureka!
Before getting desperate I had tried several adjustments and shimming of the single microswitch to no avail. I bet that I had removed and installed the switch and bracket assembly no less than a hundred times before hitting upon the right combination. All of this was done while lying on the cabin floor with head upon the rudder pedals peering into a mirror and holding a flashlight! It is impossible to directly view the switch/throttle cable from the pedestal cover, left side, right side, etc. I even pulled the avionics tray hoping to get a top down view - nope!
My solution was to use two switches mounted side by side in tandem, replacing the single narrow actuator lever with a wider double-wide actuator lever, and use the switch contacts in one switch only. The other switch is simply a spacer and helps to stabilize the actuator lever from deflecting sideways or only on one side.
An extremely important consideration during the initial set up was, "Where is the throttle actuating arm's phenolic block supposed to be when the throttles are set to idle?" I have a request in to Piper Technical Support for the official answer as it is not in the Piper Seneca Service Manual. The landing gear microswitch's range of adjustment is rather limited, so the idle position became paramount where to position the phenolic block so that the switch can be adjusted for the 14"Hg (+/- 2"Hg) operating set point. Everything is predicated on where the throttle levers are positioned for the initial setting. I had to reposition the throttle levers at idle by repositioning the engine's throttle lever arm on the air manifold assembly! This also required adjusting the throttle cable length at the rod end on the engine end of the throttle cable. I positioned the phenolic block's upper end about 1/4" from the throttle cable's outer guide tube with the throttle lever at the idle position for the initial setting. The phenolic block rides on the outer dust shield or guide tube when the throttle lever is moved from idle to full power.
Whew! Five days and counting to fix a rather simple problem due to a poor design by Piper. I'm happy to report that the tandem switch arrangement with the double-wide actuator lever (JV-91) solved all my problems, works beautifully, and more importantly - cannot impede throttle lever movement unlike the narrow actuator lever. I cannot believe it myself, but the functional check flight went off without a hitch and I didn't have to make another adjustment. I'll take being lucky on this one, especially after five days!
Sorry! Rotate image 180 degrees. Phenolic blocks at bottom right, switch upper left
Let me start off with saying unless you are involved with multi-engine training, involving single engine operations or simulated single engine operations, you'll probably never notice the landing gear warning switch's function in normal flight operations until it is too late. The switch operates the gear unsafe light and the gear warning horn whenever the landing gear is Up and one or both engines are at 14"Hg manifold pressure (idle power). The reminder to lower the landing gear may come too late in the flare during landing, at the instant when power is reduced to idle!
The problem here was that the landing gear warning horn and gear unsafe light were not working every time one or the other throttle levers were brought to idle while the landing gear was retracted. The warning switch is activated by actuator levers having phenolic blocks attached at one end to trip or operate the single switch. The V3-1 microswitch has a JV-7 Actuator Lever that is simply too narrow (.190") to reliably trip when either the left or right actuator lever's phenolic block passes beneath the switch. The two blocks (left and right) are separated by what seems to be the same or similar dimension (.180 - .190") as the width of the actuator lever on the microswitch! This is really a poor design by Piper that can be improved immensely by a wider actuator lever than the present JV-7 lever.
I had the misfortune to replace both throttle lever actuator arms (PN: 96163-00 Actuator, left & 96163-01 Actuator, right) behind the instrument panel in a most inaccessible location as what can be imagined, only to find that the new actuator arms did not correct the too-wide spacing problem between the two actuator arms. A new microswitch actuating lever JV-7 did not correct the problem either as the replacement was the same width as the previous lever.
I then tried installing two microswitches, each with their own actuating lever JV-7 and had problems with both microswitches operating at different set points. This entailed spacing the switch bracket outboard and away from the left side mounting bracket about .090" so that the centerline of the two switches was centered between the two throttle lever actuating arms.
Hmm, unable to locate a wider actuator lever for the microswitch... two microswitches operate at different times... what about two microswitches operated by a single wider actuator lever made for two switches mounted in tandem? Eureka!
Before getting desperate I had tried several adjustments and shimming of the single microswitch to no avail. I bet that I had removed and installed the switch and bracket assembly no less than a hundred times before hitting upon the right combination. All of this was done while lying on the cabin floor with head upon the rudder pedals peering into a mirror and holding a flashlight! It is impossible to directly view the switch/throttle cable from the pedestal cover, left side, right side, etc. I even pulled the avionics tray hoping to get a top down view - nope!
My solution was to use two switches mounted side by side in tandem, replacing the single narrow actuator lever with a wider double-wide actuator lever, and use the switch contacts in one switch only. The other switch is simply a spacer and helps to stabilize the actuator lever from deflecting sideways or only on one side.
An extremely important consideration during the initial set up was, "Where is the throttle actuating arm's phenolic block supposed to be when the throttles are set to idle?" I have a request in to Piper Technical Support for the official answer as it is not in the Piper Seneca Service Manual. The landing gear microswitch's range of adjustment is rather limited, so the idle position became paramount where to position the phenolic block so that the switch can be adjusted for the 14"Hg (+/- 2"Hg) operating set point. Everything is predicated on where the throttle levers are positioned for the initial setting. I had to reposition the throttle levers at idle by repositioning the engine's throttle lever arm on the air manifold assembly! This also required adjusting the throttle cable length at the rod end on the engine end of the throttle cable. I positioned the phenolic block's upper end about 1/4" from the throttle cable's outer guide tube with the throttle lever at the idle position for the initial setting. The phenolic block rides on the outer dust shield or guide tube when the throttle lever is moved from idle to full power.
Whew! Five days and counting to fix a rather simple problem due to a poor design by Piper. I'm happy to report that the tandem switch arrangement with the double-wide actuator lever (JV-91) solved all my problems, works beautifully, and more importantly - cannot impede throttle lever movement unlike the narrow actuator lever. I cannot believe it myself, but the functional check flight went off without a hitch and I didn't have to make another adjustment. I'll take being lucky on this one, especially after five days!
Sorry! Rotate image 180 degrees. Phenolic blocks at bottom right, switch upper left
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