A Weird Day

We started today in Helena, MT. It was supposed to be a fairly easy day with a scheduled 1610 departure to Seattle followed by a Missoula turn and then a Seattle-Edmonton flight arriving at midnight. Things didn't quite go as planned - for any of the legs.

On my preflight in Helena I discovered that one of the propeller blades had a substantial piece of its anti-ice heater element missing, with the rest starting to peel off. It's a common problem on the Megawhacker, but it usually gets written up before it gets that bad. Maintenance control called out contract maintenance; they used a knife to clean up the peeling part of the element and then consulted with our engineering department to determine if the airplane was airworthy. Eventually they decided it wasn't, and the airplane would need to be ferried to a maintenance base for repair. The HLN-SEA revenue flight had to be cancelled.

Seattle was be the most logical maintenance base, since the next flight for both airplane and crew was SEA-MSO. However, the ferry permit required us to stay out of icing conditions, and there was a fair amount of high level moisture between us and Seattle, so dispatch decided to send us to Boise instead. The Missoula roundtrip was cancelled, so our new goal was to make it to Seattle in time for the Edmonton flight. The Helena-Boise flight was fairly uneventful and interesting thanks to some scenery we don't normally fly over.

The repairs in Boise took about an hour; our next flight to Seattle would be an empty repositioning leg. We had just lifted off and retracted the landing gear when something interesting happened: The gear doors closed, and then opened, and then closed again. The captain and I did a doubletake and eyed the gear lights skeptically; then the doors cycled again, this time with a gear unsafe indication which lasted for a few seconds. A few seconds after that, the left gear door cycled again. By now it was clear that something was not right, so I kept the airplane slow while the captain called maintenance on the radio. The landing gear ceased its antics then, so I accelerated to normal cruise climb speed and maintenance control decided not to have us return to Boise, but divert us to Portland. We got our dispatcher to rerelease us and got a new clearance from air traffic control.

There were quite a few buildups and we were getting into IMC so I turned the radar on; true to form, it refused to operate. I tried turning it on and off a few times, to no avail. Suddenly, it started to paint a return...but it wasn't green or yellow or red or pink...it was blue!!! Neither of us had any idea that the radar was capable of displaying blue. And it wasn't a regular weather return, it was a blob that grew with every sweep of the radar until it filled the screen. We looked at each other in disbelief; I remarked that I was thinking this airplane was possessed. When we looked back, the radar was painting weather echoes with its usual color palette.

We began our descent into Portland while still east of the Cascades, and started picking up some light rime ice. Suddenly, the autopilot disconnected, the PFD displayed a flashing "IAS mismatch" warning, and several caution lights came on, including "pitch trim," "elevator feel," "rudder control," and "outboard spoilers." I handflew the airplane while the captain ran the appropriate checklist. I noticed that the captain's PFD was indicating significantly less airspeed than my own, and it was decreasing as we descended. My own airspeed was the same as the standby airspeed indicator, so I was pretty sure the captain's airspeed was wrong. Given all the gremlins on this flight, I was getting a little creeped out.

A tidbit from long-ago instrument training came to mind: "A blocked pitot tube will cause an airspeed indicator to behave as an altimeter." Suddenly I realized what had happened: the captain's airspeed indicator, presumably blocked by ice, had caused the #1 air data computer to take itself offline, resulting in the various caution lights. The checklist confirmed my suspicions and directed us to switch captain-side instruments to ADC2. Before we did so, his airspeed returned to normal and all caution lights extinguised. We continued at a reduced airspeed and I handflew the rest of the way, just to be safe, but the problem never came back. I'm guessing it melted away.

After all this, we were more than happy to part with Aircraft 416. We weren't sure that we'd be flying anymore, given how short the company was on planes today. However, we had cancelled three flights already and dispatch wasn't about to hear of a fourth! After we parked 416 at the hangar in PDX, we hurried over to aircraft 407, newly repaired after an air conditioning writeup. We flew it empty to Seattle - our third repositioning flight of the day - and quickly loaded the Edmonton passengers onboard. We departed about 1.5 hours late.

The day wasn't quite done with us, though. As we approached Edmonton, we were treated to a brilliant lightning display from storms on the east, north, and west sides of the airport. The strong gusty winds were favoring runway 12; we kept our base in tight to stay as far as possible from a strong cell just to the west. As I passed through 500' on a classic "black hole approach" to a runway with an inop glideslope and VASI, flying "solid blue bug" for windshear preparation, I realized that there were places I'd much rather be at 1:30 am on a stormy night. Oh well. The landing was passable if not silky smooth.

Tomorrow is only one leg to Seattle, then a deadhead to Portland. One leg. That should be simple enough to not screw up, right? After today, I'm wondering....