Dead Cheetah Month
I haven't written much about flying in the Cheetah because I haven't been doing any. The airplane went down almost a month ago, and it took a couple of weeks for my mechanic to get up here to troubleshoot the thing. Now, we’re waiting for parts, and he seems to be having a little trouble getting his hands on a starter relay.
The trouble started when I noticed on two successive flights that the starter Bendix wasn't cleanly disengaging after I released the engine Start button. Bill thought the starter ring gear might have some corrosion on it that was causing the hang up, so I bought some LPS1 lubricant and sprayed it liberally on the ring gear and bendix gear assemblies. But when I got in the airplane to start it up and hit the Master switch and Starter button, I got a short “hurrumph” without the prop even hitting one lick, acting like the battery had no juice in it. A second attempt seemed to drain the battery completely. Everything electrical in the cockpit went dead.
After talking on the phone with my mechanic and checking the Grumman Service manual, it was evident the first place to start was with the battery. I pulled it out and charged it up but got no better result when I put it back in the airplane and tried it again. To rule out the possibility that the battery was only taking a surface charge, I even bought another one, had Bill charge that one, and tried it. No joy. It made us think the battery relay (some folks call it the “master relay”) look like the probable culprit. So, Bill ordered a new one.
About a week later, Bill finally made it up to the Cheetah and put it in. When the electrical system stayed dead for him, too, he finally started some serious troubleshooting. He found that the starter had shorted out, and the short had fried the Starter Relay and the Master Relay with it. The large wire carrying current to the starter had also gotten pretty hot, so he wanted to replace it, too. He’d have to fabricate that, but I told him to go ahead and to replace the old Prestolite starter with a lighter weight Sky Tec starter. Not only is it some eight pounds lighter, but it is designed without a Bendix to eliminate that failure mode. He’s already got that but we’ve been stalled waiting for a starter bendix to arrive. We’re hoping it gets here early next week.
The trouble started when I noticed on two successive flights that the starter Bendix wasn't cleanly disengaging after I released the engine Start button. Bill thought the starter ring gear might have some corrosion on it that was causing the hang up, so I bought some LPS1 lubricant and sprayed it liberally on the ring gear and bendix gear assemblies. But when I got in the airplane to start it up and hit the Master switch and Starter button, I got a short “hurrumph” without the prop even hitting one lick, acting like the battery had no juice in it. A second attempt seemed to drain the battery completely. Everything electrical in the cockpit went dead.
After talking on the phone with my mechanic and checking the Grumman Service manual, it was evident the first place to start was with the battery. I pulled it out and charged it up but got no better result when I put it back in the airplane and tried it again. To rule out the possibility that the battery was only taking a surface charge, I even bought another one, had Bill charge that one, and tried it. No joy. It made us think the battery relay (some folks call it the “master relay”) look like the probable culprit. So, Bill ordered a new one.
About a week later, Bill finally made it up to the Cheetah and put it in. When the electrical system stayed dead for him, too, he finally started some serious troubleshooting. He found that the starter had shorted out, and the short had fried the Starter Relay and the Master Relay with it. The large wire carrying current to the starter had also gotten pretty hot, so he wanted to replace it, too. He’d have to fabricate that, but I told him to go ahead and to replace the old Prestolite starter with a lighter weight Sky Tec starter. Not only is it some eight pounds lighter, but it is designed without a Bendix to eliminate that failure mode. He’s already got that but we’ve been stalled waiting for a starter bendix to arrive. We’re hoping it gets here early next week.
posted by Andy Foster at 5:14 AM
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