Forced Landing #2
By: Jim Hayward
On the evening of July 10, 2001, an A&P friend, Doug Derby, and I took off from my strip about 7:15 pm. Doug had been wanting to go with me in the Challenger for a while and our schedules finally coincided so we could. Thunderstorms had been forecast for the afternoon and evening but had not materialized other than some overcast skies, so we went.
We flew along the foothills east of I-90 up by Sturgis, then back out over the plains towards a crop duster's place just north of (daughter) Lynette's Place.
The old guy was home so we landed for a short visit. We had about 20 minutes before sunset so only stayed a few minutes. Departing his strip, we headed back toward Rapid City, overflying Lynette's homestead and on over past Doug's folk's place.
About a minute or so north of town, the Rotax suddenly dropped to about 4000 rpm. At first I thought Doug had moved around in his seat and inadvertently moved the throttle since the Challenger can be flown from either seat. I reached down to increase it only to find it was where I had left it!
The EIS instrument package's alarm went off and the display switched to the EGT screen showing them at 1154 degrees. My next thought was fuel starvation, so I hit the choke. On the Rotax's Bing carbs, the choke is actually a fuel enrichener that allows more fuel flow instead of restricting the airflow. Well, this had no effect nor did further working of the throttle.
One of the fun things of flying the ultralight family of aircraft is being able to fly "low and slow." One byproduct of this "fun thing" is that your options can be very limited should a malfunction occur. We were about 600 feet AGL when the engine reduced power, losing altitude slowly but surely. We had to do something.
It takes about 5000 rpm for my Challenger to maintain altitude with 2 on board, so I started looking for a spot to set down. There was about a mile stretch of straight road ahead of me so I set up for a landing on it.
No more had I set up than a car pulled out and turned north towards me. "Damn...", I thought. Doug's voice came over the intercom, "You got a spot picked out?"
I looked around and said, "Yeah."
In the newly subdued light of dusk, I had spotted this hilltop off to my right so I cranked 'er around and set up for it. The engine never quit, and we headed on down for the hilltop.
Okay, here we go ... back off with what power we have ... 55 mph ... looking good ... not much further ... oooh nice, the top looks pretty level ... 50 mph ... uh oh, there's a fence ... a little power ... over the fence ... chop the power ... touchdown ... good ... rollout ... BAM! ... BAM, BAM! ... MAN! This thing's like riding a buckin' bronco! Geez! There are rocks all over the place!
We get stopped, I shut the engine down and ask, "You okay?"
Doug says, "Yeah."
We get out and I go back to see if I can find anything wrong. I look things over expecting and hoping to find maybe a wet fuel line or anything that might give us a clue as to what happened. Nothing is forthcoming so we get back in and I crank it up. It runs fine so I give it full throttle... no problem!
We start taxiing around to find a place to either decide to leave it or try taking off. I thought that if it was a fuel pickup blockage of some sort, it had cleared itself with the rough landing. A few more full power runups gave the same performance I was used to getting from the Rotax. Okay, taxi some more, we gotta find a place to try a crowhop.
As we're taxiing over these damn rocks, the nose just gently drops as I hit one rock too many, and the nose gear collapses.
Doug says, "We're done aren't we?"
"I think so."
We get out to find the nose gear folded back under the belly, fabric torn pretty good and stringers bent from rocks. We find a dug out area at the base of a hillside and drag the Challenger over to it, parking it with the tail uphill and the mains nestled in the dug out area. I wanted it protected as much as possible if the storms materialized during the night.
We plant the tiedowns and tie it off then walk the 1/3 mile or so to the road and another 1/2 to 2/3 mile to a housing development. We find a house with the family watching TV and knock on the door. A fellow in his late 20's comes to the door.
"Yeah?" he asks.
Doug says, "Could we use your phone?"
"What's the matter?"
"Uhh, we broke down and need to call our wives to come get us."
"Broke down... where?"
"Oh, just up the road a piece." says Doug.
"What happened, you run out of gas?"
Doug looks at me and I look at him with a bit of a grin. "Yeah, you might say that," Doug replies with a chuckle.
The guy looks at us and I say, "Our plane went down and we need ..."
"YOUR PLANE WENT DOWN??? WHERE??? ANYBODY HURT??? YOU NEED AN AMBULANCE??? YOU GUYS OKAY??? WHAT HAPPENED???"
The guy was really excited now!
"Oh, no, we're just fine," I replied, "The engine just lost power and we landed in a pasture. We just need to call our wives to come get us."
He went and got the phone. It was now about 9:20 pm and knowing Linda usually gets off work at 9 pm, I was sure she would be home. Ring ... ring ... ring ...
"Hello," answers this familiar voice.
I try a nonchalant voice ... "Hi, Hon."
She comes back with, "Where ARE you ???"
I say, "You know where Tim's sister lives?"
"Uuh huh ..."
"Well, we're just down the street from their house and we need you to come get us."
"JIMBO, what happened?"
"Uuh, we lost power on the engine and had to set it down in this pasture."
"I KNEW something was wrong! I've been going nuts waiting for you 'cause you've NEVER been out this late with it."
I try to reassure her, "We're just fine but the plane's broke."
"Broke? HOW ???," she asks.
"The nose gear collapsed while we were taxiing around ... the place was full of rocks and we didn't see them due to the grass and all."
"Ohh, JIMBO...okay, I'll be there as soon as I can."
"Okay, thanks Honey, bye." I say rather meekly.
I ask Doug, "You gonna call your wife?"
"Nope, not right now," he replies.
We got it trailered back home the next day. I had to go out of town for work. It was Friday before I returned and could work on it.
I pulled the fuel system completely out and apart, everything from the tank to the fuel pump to the carbs, looking for anything that might have caused the problem. I found nothing ... the system was completely clean ... no water, grime, junk, or anything else. Additionally, I found there was a slot cut in the end of the pickup tube which would have prevented any blockage in the first place.
With finding nothing and some EAA folks suggesting that it sounded like carb ice, I e-mailed the weather service to see what the temp/dew point was for that evening. The EAA people had said that as little as 2 to 3 degrees difference could cause icing in temps as warm as 85 to 90 degrees.
The weather service wrote back that at 8 pm, the temp was 66 degrees and dew point 63 degrees, with 9 pm showing 64 / 63. Gee, it was cooler than I thought.
Well, it certainly looked like icing was the culprit, but I still didn't want to believe it due to the answers I had from the guys that had flown these things, literally for years.
In my 30+ years of aviation, the Challenger was the first plane I'd ever flown that didn't have carb heat. In questioning it, I was told that due to the design of the 2-stroke, it "spits" fuel back into the carb throat thereby preventing any ice from forming. Furthermore, the Bing carburetor is a variable venturi and needle design so it is inherently not susceptible to icing.
So, I put my dilemma out to the Challenger e-mail list and got a reply from Bob Robertson, a Rotax mechanic in Canada. He told me he had seen one instance of icing on a Rotax with the Bing carb a few years ago.
He said there is a baffle in the throat just in front of the fuel outlet that creates the low pressure necessary to draw the fuel up out of the bowl. Ice can form there and cause the baffle to lose it's ability to create the low pressure and draw up the fuel.
Well, it sure looks like that was the cause of my fuel "starvation" and the cause of my EGT's going up so high when we lost power.
There are a couple of aftermarket heaters for the Bing carbs, but I read an article that you can't just turn them on and suddenly have the ice be gone. You have to have them on for a while before you expect the ice to form.
I'm looking at a way to heat the body faster and will report my findings to the Challenger list if and when I do. No one out of the 450+ membership on the list reported that they use any kind of heater.
Right now, I just don't fly if the temp/dew point are closer than about 8 to 10 degrees apart.
The Challenger has been flying again for about a month (as of mid-August, 2001) with no more problems. I'm a lot more aware of the temps now and have installed the probe of an indoor/outdoor thermometer on the carb body to do some research into our operating conditions. I'll report the results of this to the Challenger list for anyone else's information and use.
Doug wants to go again and said he was very impressed with the plane. He felt that had we been in a factory-type aircraft, the damage would have been substantially more, the field probably would not have been long enough, and who knows what else could have happened?