The International Cessna^® 170 Association

Recently I had to pull my ignition apart as my aircraft didn't come with the right key. Being tasked with buying a $300 ignition or getting a key from a locksmith, I tore the switch apart, and it turns out we have a "Wafer Tumbler Lock". As soon as I seen this I realized it can be easily picked with a paperclip and a little tension on the lock. http://www.lockpickguide.com/waferlocks.html Real shame our aircraft can be picked so easy!

My father in law has a hardware store, and having worked there since I was a kid I was familiar with cutting keys and keying house locks. I was even introduced to "bump keys", over the years by a customer. (If you never want to sleep again click here! http://www.youtube.com/watch?v=pwTVBWCijEQ) So after getting the lock apart and having a key that was close but not perfect, I decided that I could easily adapt the key I have, or a new key blank (blank Y11) to fit the lock fine. So I am now going to try to write a little DIY for anybody having the same issue.
CAUTION REMOVING THIS SWITCH WILL MAKE YOUR MAGS HOT!!! A LARGE SIGN ON THE PROP WOULD BE A GOOD IDEA!
Step 1. Remove Round ring on front of dash. It should turn off counter-clockwise, and may need some plyer assistance.
Step 2. Remove wire-keep on the back of the switch with a straight slot.
Step 3. Remove back cover of key switch.
Step 4. Label the wires on the back of the switch with masking tape. The switch is labeled Left Right, GND. Mine had one wire to left and right and two to GND.
Step 5. For safety tie the P-Leads together and place a jumper to Ground, until they are re-connected to the switch!
Step 6. On a clean flat surface with a white papertowl down slowly remove the backing plate, by removing both straight slot screws on the back of switch. Use care to not lose the two springs and two brass clips which will now fall right apart.
Step 7. With a magic marker mark the orientation of the black rotating disk to the side of the case. Also mark the position of the key switch on the front of the switch with a small mark. This shouldn't matter as it seems the switch will only go back together the proper way.
Step 8. Remove the one straight slot screw in the black rotating disk and note that that the center is keyed to the switch and will only go together in one way.
Step 9. The tumbler will now fall right out of the key.
Step 10. Note that without your key all the tumbler pins stick out into the keyed channel. Insert your close key or key blank (Y11) into the switch and note that all the pins have to be flush on both sides for the tumbler to rotate. You can also note that there are 5 pins and that means 5 peaks on your key. Changing these pins is how you would "rekey" the lock.
Step 11. I am fortunate enough to have access to an old fashion key cutting machine, but if you don't have access to one you can use a file to perfect the peaks and valleys to make your key.
Step 12. Re-Assemble
Step 13. Test Left, Right, Off and make sure you can can't pull the key out unless it's off.
Step 14. Drink Beer and admire your work and the fact that an hour just saved you $300 bux!

I hope this helps somebody else. Pictures attached.

Randy Hentz

P.S. Feel free to move this post (and any others I misplace) to the maintenance section or it's proper home.

j3pup wrote:... Real shame our aircraft can be picked so easy!...

Even with a good lock, it's a simple matter to pull the door-hinge-pin to gain access, and cut the P-leads. Who needs a key? Real aircraft security requires a throttle-lock or prop-lock.

j3pup wrote:... Feel free to move this post (and any others I misplace) to the maintenance section or it's proper home.

This IS the maintenance section.

Randy,
I think you should consider adding some heavy emphasis that the Mags are hot during the time you have the switch removed. Perhaps some alternate way of grounding them and a big sign on the prop.

Great Point Will Do!

[quote="]...
CAUTION REMOVING THIS SWITCH WILL MAKE YOUR MAGS HOT!!! A LARGE SIGN ON THE PROP WOULD BE A GOOD IDEA!
....[/quote]

Anytime the P-leads are disconnected from the switch, for ulitmate safety they can be tied together and a jumper placed to Ground, until they are re-connected to the switch. GREAT CATCH, John!

I added all the suggestions, thanks!

Another good idea is never pull the prop through in the direction of fire (the impulse won't catch then)......Don't worry about the old stories of braking veins of the vac pump....That is, (in most cases) an old wife's tail .......Brad

I just thought about something else.....when in flight school, in order to get free flight time, I remember going to Mid-Way, with a bucket of keys......The owner of the flight school said (Cessna only builds a certain amount of keys.....one will fit) and sure enough...within twenty keys we had the door open and the airplane running.....(I guess I just then, became a repo man) ....Brad

There are only 5 wafers in the lock, whoever keyed mine was lazy and used 2 of one size and two of another so it wasn't even much of a challenge to cut the key. By the way the key worked great in the doors too.

I have a friend who claims he has a camper top key that starts any Cessna....

j3pup wrote:...I have a friend who claims he has a camper top key that starts any Cessna....

I have a set of wire-cutters that will do that and more!

Brad Brady wrote:Another good idea is never pull the prop through in the direction of fire (the impulse won't catch then)......Don't worry about the old stories of braking veins of the vac pump....That is, (in most cases) an old wife's tail .......Brad

Especially not harmful to a 170 with VENTURIIS !!!

Nice!

J3pup


Thank you for the informative pictures of Ignition switch disassemble.

Especially in naming the tumbler style as "wafer tumblers" as opposed to round pin type in home door locks.

The internal wiping contacts seem to be robustly designed/ built with brass alloy that will last another 67 years.

Regards