Random Failures

[Wayne Conrad 989233]

For about a month I've been flying X-Plane online. It's taken some adjusting, but there are some neat things about it. One of the neatest is X-Plane's failure model. I've got it set to deliver a failure on the average of once every 1000 hours. A failure could be fairly big, or fairly minor. It could be an engine, and instrument, a control cable. So far I've had three failures and one bird-strike while flying online.

 

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My first X-Plane random failure came while I was on the final approach segment for a VOR approach somewhere in SOCAL. It may have been KEMT. I was plugging along waiting for the right place to start my circle-to-land when the engine started racing. The tach was red-lined, and yet the prop spun down to a stop. Broken drive-shaft! Had there been a controller online, I would have declared an emergency and landed off-field, but there wasn't, and it really was a fun approach that had gone very well. I reset the failure and continued the approach. Yeah, I wimped out.

 

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Then there was the time I was doing patterns with another plane at John Wayne. Climbing out from 19L, a flock of birds flew right across my flight path. I pushed the nose down to try and dive under them, but heard the sickening splats of multiple bird strikes. About half of my windshield was obliterated, a mess of crazed plexigl[Mod - Happy Thoughts] and bird parts.

 

"Tower, Piper 129P. This will be a full stop--I've had a bird strike"

"Piper 129P, roger. Do you have positive control of the plane?"

"Affirmative, Piper 129P"

 

On downwind I thought better of using the flaps. Not knowing what the birds might have smashed, I decided I didn't want to move any of the movable things on the plane. I opted for an extended downwind to make the flat no-flaps approach easier. I'm not great at no-flaps approaches.

 

"Piper 129P will make an extended downwind"

"Piper 129P, roger, about how far?"

"About a mile and a half, Piper 129P"

"Piper 129P, roger. Runway 19L, cleared to land"

"19L cleared to land, Piper 129P"

 

I came in a bit hot and used up more than half of 19L. In hindsight, I should have requested 19R. No reason not to take every safety margin I can when the plane is in an unknown state.

 

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The second failure was when in the pattern with another plane at Santa Monica (KSMO). Do you get the idea that I like traffic patterns? Practice, practice, practice. I had just turned crosswind and was nearing pattern altitude, so I started to throttle back. The throttle didn't do anything. The tach showed full RPM, the prop was spinning, and I was still climbing like mad. This would be a good place to declare an emergency, but I decided not to. The other pilot was a greenhorn who was doing really well--I didn't want to toss a spanner in the works for him.

 

"Tower, Piper 129P will be full stop. My throttle is stuck, but I should be able to land normally."

"Piper 129P, roger"

 

I let the airplane climb on downwind to well above pattern altitude before I pulled the mixture to idle-cutoff to turn the engine off. I was so high that I needed to extend my downwind to be able to lose the extra altitude, but I extended it too far and was going to come up short. The prop was windmilling, so I crossed my fingers, pushed the mixture back in, and the engine roared back to life. Just five seconds of that was enough to make up for my bad approach and let me land on the runway. I rolled onto the gr[Mod - Happy Thoughts] beside the runway.

 

"Tower, Piper 129P is clear of the runway. I'll leave it here on the gr[Mod - Happy Thoughts] while I go find a mechanic."

"Piper 129P, roger."

 

When I pulled up X-Plane's failure menu, it showed that the throttle was indeed stuck on "full go." I cleared the failure, stretched my legs, and then called tower up:

 

"Tower, Piper 129P. The mechanic found his daughter's barbie doll jammed in the throttle linkage. It's all better now, and he owes me a six pack."

"Piper 129P, roger, I hate it when that happens."

 

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The most recent failure occured while flying an approach. Center had cleared me for the approach, and I was having a good time, with my heading and altitude within PTS and everything going smooth. Maybe I'd even remember to start the timer this time. This approach has a holding-pattern course reversal, so over the VOR I turned for the teardrop entry and started my descent. After I finish dialing in the OBS for the inbound course and make sure everything's good, I look at the altimeter to see how the descent is going, and I discover I haven't descended at all. I'm still at cruise altitude. Oh, dang! I always forget something. But, wait. My throttle is at descent power, my VSI shows 500 fpm down, my airspeed is normal, my AI shows that I've got a slight nose down atittude. I am descending.

 

Ok, what's failed here? Is it the static system? No... if it were, my VSI wouldn't be showing a descent, and my ASI wouldn't be working right either. It's got to be just the altimeter that's failed. Oh, well. I started a turn towards the field.

 

"Center, Piper 129P is going to have to break off this approach and proceed visually to the field. My altimeter has failed."

"Piper 129P, roger. Would you like the visual approach?"

"Negative. Piper 129P cancel IFR"

"Piper 129P, IFR cancellation received."

 

Center then asked me to verify my altitude. "Indicating 5000"

"Piper 129P, Your mode C shows you at 3700. Squawk standby"

 

I don't know if center misunderstood and thought that my mode C was unreliable, but I think it was working fine. It looks like the X-Plane transponder has its own altitude encoder built in. Or perhaps since my altimeter was no longer working, center could no longer verify my mode-C readout and wanted my mode-C off for that reason. But knowing that the mode-C keeps working after the altimeter fails will be handy if this failure ever occurs in IMC. I can complete an approach in the soup if the controller can keep an eye on altitudes for me. Over the short haul, with the airplane trimmed out, it's not hard holding a relatively level altitude using just the VSI.

 

Center then handed me off to SOCAL, who gave me my landing clearance. It was interesting entering the pattern and landing with no altimeter. Not as hard as I thought--everything in the traffic pattern is by angles: If you are above pattern altitude but turn downwind when the runway is the right angle below the horizon, you'll be farther away from the rightway by just the right amount. If you are below pattern altitude but turn downwind when the runway is at the right angle below the horizon, you'll be closer to the runway by just the right amount. And so on. I have no idea how close I was to pattern altitude, but it worked out like a normal landing.

 

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That's three failures since I started flying x-plane online. That's way more than an everage of one per thousand hours. Statistical anomaly? Could be. Random events sometimes form seemingly non-random patterns. Responding to an unexpected failure adds a bit of juice to a flight, and is one of the reasons I like x-plane for most of my flying.

[Ian Elchitz 810151]

As usual - I enjoy reading your thoughts on X-Plane. Thanks for sharing Wayne.

[Anthony Belton-Ford 102141]

i have random failures on fs2004 in my 737-700 but does anyone know how to set failures like evry so and so times on fs2004