Too smug for comfort

5469
© CASA

Name withheld by request

Another very experienced pilot and I were flying a Conquest back to home base after dropping off a load of passengers. We knew the aircraft, route and airspace like the backs of our hands, we both had a couple of thousand hours in the Conquest, and normally flew single-pilot IFR, so two-crew operations were a perfect opportunity for a good chin wag (and, in hindsight, for some serious mistakes).

We did everything without really thinking about it and completed the checks in record time.

As we turned onto heading and climbed through 4000 feet I noticed that the runway rising indicator and the glide slope indicator were stuck together inside the artificial horizon. The aircraft was flying as per normal and it was a gin-clear day all the way home so I did not see it as a major problem. Having never seen this bizarre malfunction before I casually remarked how odd it was. As we continued home, we started trouble-shooting the system; pulling circuit breakers, changing modes, testing the radar altimeter function, all in an attempt to correct the minor inconvenience.

Route clearance was given and I stopped playing with the knobs and switches for long enough to read back the clearance and dial it into the GPS—but then I noticed something else out of the ordinary. I didn’t have the correct way point in the GPS …

I immediately realised my mistake; I had simply reversed the route (a one-way route) in the GPS and was cleared back home via another one-way route that kept inbound and outbound aircraft separated as they funnelled into our capital city. ‘What an idiot! Ah well, no problem.’ In six seconds flat I was able to dial up the route required, check it over and get us heading in the right direction. Problem solved, back to chatting about how we could fix our annoying indication issue. Sadly, my complacency had made me miss a major red flag.

We settled into the cruise at FL250 and, having exhausted our options for the artificial horizon anomaly, left it at that and started busily planning lunch, his retirement and my upcoming job interview.

Along the way we were told to lose more than six minutes for our arrival point (a major blow to our lunch plans) and we pleaded with the controller to try and slot us into another runway or squeeze us into the pattern a little earlier. At 350 knots we were keen to keep that ground speed up, but the controller was not having a bar of it and asked us if we would like vectors—the internationally recognised way for controllers to signal the impending end of a conversation.

Disappointed, I declined and pulled the power levers to flight idle.

We resumed our conversation and watched as the ground speed peeled back from an enjoyable 350 knots into the depressingly low 200s.

As we approached our arrival point a red annunciation CABIN ALTITUDE lit up on the warning panel. Neither of us had experienced this before but it meant that the cabin altitude was above 11,500 feet. At 35,000 feet the Conquest can hold 10,900 feet cabin altitude, so this was a definite surprise, considering we were 10,000 feet below that.

We stopped discussing trivialities and started trouble shooting. He pulled the circuit breaker that allows the passenger oxygen masks to deploy (even though they are one hell of a thing to replace in the roof lining) and increased the cabin heating (this helps to increase cabin descent), while I set the cabin in a descent, powered up the engines to provide more bleed air and started our descent a little early to help the entire process out.

Once we got the cabin descending the light went out and we continued home, using the SOPs in a more professional manner.

The cabin had been in a slow descent from the moment I pulled back the power (a cold cabin and very low power setting means the pressurisation system struggles to maintain altitude). If we had been paying attention one of us would have scanned the cabin altitude and noticed the issue earlier.

If we had been paying attention …

Two very experienced pilots flying an aircraft that can easily be flown by just one, on a perfectly clear day, in familiar airspace, had managed through simple inattention to get behind the aircraft. As says the law of sod; right when you think everything is fine is when it will decide to bite.

Aircraft will do that if you don’t keep an eye on them and yourself.

Stay steely and watch out for red flags whatever and whenever you are flying.

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