Runtoeat Posted July 23, 2013 Report Share Posted July 23, 2013 Yesterday, I experienced a scary but good learning experience that all pilots who are new to LSA with Rotax engines will benefit from. It was a hot day in Michigan, around 90F, and I was anxious to get up in the air before the temps rose further. The hangar owner stopped by while I was getting ready to pull out of my hangar and chatted with me. Since he had recently sold his Mooney, he was on withdrawal from not having an airplane to fly and asked if he might go along with me. I said "sure" and we got in and prepared to start up. Showing my passenger how to buckle in, get his headset adjusted, how to egress, where the 'chute pull handle was all threw me off. I just didn't feel like I was completely on my game plan. Due to this, I tried to deliberately go thru my normal procedure. I pulled my checklist and went thru it. My passenger talked to me on my first attempt, so I went thru the checklist a 2nd time. Time to start the engine. Hmmm, really hot outside but a cold engine, maybe just a small amount of choke. Got started, taxied out. Runup, no issues. Once in the air, find a place to go. OK, picked out a small airport in Brighton, Michigan with a 50' wide runway that looks like a sidewalk from the air. Downwind OK, now base and now on final. Pull power and set up. All of a sudden, strong vibration from my engine which is something I've never experienced. Along with the vibration, my rpm's dropped to 1500rpm instead of the normal 2100 rpm idle I normally see on final with power pulled. Then the alternator light came on and the engine was starting to quit on me. I put in some power and the engine immediately came back to life and the ibration went away. We continued our approach and landed. Runup on the ground indicated all was normal. Inspection of the plane showed nothing out of place. Startup took an unusually long time to get the engine to properly fire but then it seemed to run fine. Runup at the hold short again showed no concerns. We took off and returned home. On my landing, the same vibration with engine rpm dropping occured. This time, I added throttle and the engine did not start stumbling and indicating it would soon stop. Once back to the hangar, I took off the cowls and my mechanic friend and I did some investigating. Anyone know want to venture a guess what I found the problem to be? Link to comment Share on other sites More sharing options...
sandpiper Posted July 23, 2013 Report Share Posted July 23, 2013 You left the choke partially on because you were distracted. Link to comment Share on other sites More sharing options...
CT4ME Posted July 23, 2013 Report Share Posted July 23, 2013 Sounds a bit scary, and probably not a good introduction to LSAs for your friend :blush: I'm with John... choke? tim Link to comment Share on other sites More sharing options...
FredG Posted July 23, 2013 Report Share Posted July 23, 2013 Dick, the suspense is killing me. I'm also with John and Tim, choke? Link to comment Share on other sites More sharing options...
Adam Posted July 23, 2013 Report Share Posted July 23, 2013 I grew up in Birmingham, lived in Ann Arbor twice and Brighton the longest... Brother, parents and 2 sisters still in Brighton / Howell. I know that "sidewalk" well... :-) I'll vote choke along with the others (especially since you emphasized "small amount of choke for that cold engine") Very good lesson! Link to comment Share on other sites More sharing options...
Doug G. Posted July 23, 2013 Report Share Posted July 23, 2013 Dick, I don't remember what you fly, but the choke makes the most sense to me. Link to comment Share on other sites More sharing options...
mocfly Posted July 23, 2013 Report Share Posted July 23, 2013 Ignition cable connector on one or more cylinders Link to comment Share on other sites More sharing options...
Runtoeat Posted July 23, 2013 Author Report Share Posted July 23, 2013 You guys are too good at this. I thought that there would be one or more who would offer up carb debris in the float bowls. I've read so much about others having a problem with engine stumbles after the rubber change, this was my first thought. Then, I reasoned that this would make matters worse under higher fuel demand and this was not happening. Instead, more throttle helped the situation. Poor or intermittent ignition or fouled plugs then became my next suspected cause. Following this suspicion, we pulled first the top plugs and then the bottom plugs. To our surprise, all plugs were black and sooted up. Hmmmm, this looked like too much fuel? What would cause too much fuel? Back to carb bowl debris? No, debris wouldn't do this, it would do the opposite and restrict fuel. Then the thought hit me and I immediately looked inside the cockpit to check my choke. Yup, you guys got it, I left the choke on. Now things made sense. Unlike a normal choke which restricts airflow to the carb, the Rotax Bing carb choke adds fuel instead of restricting airflow and is sometimes called an "enrichener". Although not totally sure about the various fuel circuits thru the Bing, I believe that the engine will load up at idle but will run fine on mid to high range throttle when the choke is left on. Perhaps it was because of the added distraction of my unexpected passenger? Maybe it was because the hot ambient condition caused me to forget about something I normally do when it's cold outside? John got it right not only for the mechanical cause but also observed that distraction was the primary cause for this. I suspect that all of you also could see that the root cause was my distracted state. Interesting that something as simple as having a passenger come along might cause me to forget to close the choke after taking up so many other passengers but it appears that this is the case. FWIW, I will add "Close Choke!" (exclamation included) to my check list and hopefully, this will not happen again. Link to comment Share on other sites More sharing options...
Roger Lee Posted July 23, 2013 Report Share Posted July 23, 2013 The enrichers works up to about 3500 , but after that there is no affect. Next time you fly and you are at cruise rpm apply the choke, Nothing will happen. So when he reduced power back to the lower idle rpm's the choke enriches the fuel circuit and caused his poor running and black wet plugs. Good diagnosis guys. Link to comment Share on other sites More sharing options...
WmInce Posted July 23, 2013 Report Share Posted July 23, 2013 The enrichers works up to about 3500 , but after that there is no affect. Next time you fly and you are at cruise rpm apply the choke, Nothing will happen. So when he reduced power back to the lower idle rpm's the choke enriches the fuel circuit and caused his poor running and black wet plugs. Good diagnosis guys. Some sharp guys on here. Well done! Link to comment Share on other sites More sharing options...
mocfly Posted July 23, 2013 Report Share Posted July 23, 2013 If operated correctly there really is no reason to have the choke in more than the time it takes to get the Rotax engine started. While increasing Power up to 2000-2100 rpm slowly close the choke. And leave the engine at this rpm until temps are up. This way you never forget to close the choke. Link to comment Share on other sites More sharing options...
Runtoeat Posted July 23, 2013 Author Report Share Posted July 23, 2013 Chris, you may have hit on the reason I left my choke on. I normally start with choke which is set to operate my engine at 2400rpm. I wait about one minute after start and then begin to reduce choke while increasing throttle to maintain the 2400 rpm and hold this rpm until engine oil temp is at 120F. During this particular flight, I opened the choke slightly thinking I should go easy on the choke to prevent flooding the engine due to the heat. This setting started my engine but didn't provide enough to get the engine to 2400 rpm so I added some throttle. Upon reaching operating temp, I pulled the trottle back but not the choke - probably due to being distracted. It appears that the small choke setting didn't hold my idle rpm up much above 2000 rpm which I didn't think was abnormal due to conditions. As the engine heated up during flight, it became more sensitive to the added fuel the choke provided. When I went back to idle preparing to land, this is where the problems started. Thanks for your observation. This is probably a reason that I would not need to add to my checklist but I'm still going to do this. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 23, 2013 Report Share Posted July 23, 2013 We are not a bunch of geniuses, we are instead a bunch of geezers who have gone flying with our enrichers open. Link to comment Share on other sites More sharing options...
Runtoeat Posted July 23, 2013 Author Report Share Posted July 23, 2013 Gotta get rid of that pair of shorts I have with the broken zipper......! Link to comment Share on other sites More sharing options...
Jim Meade Posted July 23, 2013 Report Share Posted July 23, 2013 Yet another reason to emphasize the in-flight and approach checklists, which we CFI's tend to woefully under teach. If one doesn't like a paper checklist, a flow will work. Start at top center and touch that heat is set and carb heat is in (or set). Come down and run fingers across breakers feeling that they are all in Come to center and touch fuel valve open, then down to touch choke set, throttle as desired and flaps set. Do this before take-off, when entering cruise phase (perhaps when flaps fully retracted), on descent and again sometime in the pattern. Teaching in the pattern is a good way to not properly integrate checklists. When possible, we should frequently hop to a nearby field and force use of the checklists as we would want to be done on a typical cross country flight. Link to comment Share on other sites More sharing options...
sandpiper Posted July 23, 2013 Report Share Posted July 23, 2013 When I went thru Army rotary wing flight school they stopped having us use a written checklist when we were in our final phase qualifying in the Huey. They taught flow and if you needed a checklist on your final ride, you flunked. This was in 1969. The reason was at that time we were all going to get 30 days leave then go to Viet Nam. The feeling was that if you had to deal with written checklists with incoming, particularly at night, well, you get the picture. Just to be clear, no, I never went and never saw combat. Our class was the first to get a 6 month stateside delay since they were winding down. My six months turned out to be the rest of my 3 year commitment. I missed an opportunity for a unique experience, one that I was probably better off without. Link to comment Share on other sites More sharing options...
WmInce Posted July 23, 2013 Report Share Posted July 23, 2013 When I went thru Army rotary wing flight school they stopped having us use a written checklist when we were in our final phase qualifying in the Huey. They taught flow and if you needed a checklist on your final ride, you flunked. This was in 1969. The reason was at that time we were all going to get 30 days leave then go to Viet Nam. The feeling was that if you had to deal with written checklists with incoming, particularly at night, well, you get the picture. Just to be clear, no, I never went and never saw combat. Our class was the first to get a 6 month stateside delay since they were winding down. My six months turned out to be the rest of my 3 year commitment. I missed an opportunity for a unique experience, one that I was probably better off without. John, Ft. Wolters . . . 69-5 . . . tan hats . . . and you? Bill I. Link to comment Share on other sites More sharing options...
Jim Meade Posted July 23, 2013 Report Share Posted July 23, 2013 So - you're the guys who weren't there to pick me out of that rice paddy! Link to comment Share on other sites More sharing options...
WmInce Posted July 23, 2013 Report Share Posted July 23, 2013 So - you're the guys who weren't there to pick me out of that rice paddy! Thank you for your service there, Jim. Link to comment Share on other sites More sharing options...
sandpiper Posted July 23, 2013 Report Share Posted July 23, 2013 Bill, Class 69-24. RLO's so we didn't have some of the harassment you had and we were on PD the whole time so it was a blast!. I forget the hat color. Jim, What rice paddy? Didn't see any at Hood . I would have gone but the kept me at Hood for a big project testing FLIR. After that I was out of sync with my classmates who had already gone. I called branch about every 4 months bugging them for a transition enroute but they ignored me until one month before ETS when they called to offer an OH-6 IP transition enroute. I politely declined. If they had offered Snakes or Chinooks they would have had me. The top 10% of 69-24 was supposed to have choice of transitions but I didn't. I think being Engineer branch had something to do with that. Maybe if I had been Infantry or Armor it would have been different. And, I might have been one of the 50% of my class that came home in a box. Link to comment Share on other sites More sharing options...
2FlyAgain Posted July 23, 2013 Report Share Posted July 23, 2013 Thank you to all who served...in whatever capacity! Link to comment Share on other sites More sharing options...
Doug G. Posted July 23, 2013 Report Share Posted July 23, 2013 We are not a bunch of geniuses, we are instead a bunch of geezers who have gone flying with our enrichers open. I don't mind the geezer comment, but I haven't been flying long enough to have made this mistake - yet! Link to comment Share on other sites More sharing options...
Runtoeat Posted July 23, 2013 Author Report Share Posted July 23, 2013 Most times, we are not aware that we are talking to vets but personally I'm glad when one lets me know so I can thank them for their service. I've said it before on this forum but never tire of saying it. Thank you. Link to comment Share on other sites More sharing options...
Runtoeat Posted July 23, 2013 Author Report Share Posted July 23, 2013 Just opened up the August issue of AOPA Pilot mag and my jaw dropped when I looked at the articles and read Barry Schiff's column titled "Interruption of Routine". What an appropriate article for this thread. Jim, I've heard about using the flow routine and now that you and John have described how it's done, I would much prefer doing this than going over a paper checklist. I'll make the committment to start training myself to do this. Thanks. Link to comment Share on other sites More sharing options...
WmInce Posted July 23, 2013 Report Share Posted July 23, 2013 Just opened up the August issue of AOPA Pilot mag and my jaw dropped when I looked at the articles and read Barry Schiff's column titled "Interruption of Routine". What an appropriate article for this thread. Jim, I've heard about using the flow routine and now that you and John have described how it's done, I would much prefer doing this than going over a paper checklist. I'll make the committment to start training myself to do this. Thanks. Generally speaking, checklists are usually "follow-ups" to performing a flow pattern. Distractions can interrupt initiating or completing a flow pattern, so the checklist backs it up. Flows are done by memory . . . checklists are "read and do." Link to comment Share on other sites More sharing options...
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