Barrier Trip take 2

After being thwarted by a faulty aircraft, we rescheduled our trip to Great Barrier Island and hoped the weather would be nice to us. We were greeted with a superb day, with a large anticyclone covering most of the country. Hamilton had been covered in fog most mornings due to the slow moving air, but fortunately for us it had all but gone from the airport by 10am. After a quick scan of my logbook I realized I was not current in an Archer so I had to do three circuits in UFS first before I would be able to carry passengers.

The Hamilton circuit was as busy as I have ever seen it, with 6 aircraft doing circuits and commercial flights coming and going. I thought my circuits were OK, except I still tend to fly too close to the runway on base. Something I shall work on.

Once that was done I taxied back to the Club and filled the plane. We loaded up, grabbed some lifejackets, fiddled with them to put them on ( love how you just clip them around your waist and leave them unless you need them). I started UFS up, got taxi instructions, asked for the tarmac runway (I think I might have slightly annoyed the controller) and we took off. The first thing I noticed is how different the climb performance is with 2 extra people, their luggage and full fuel tanks. The ride was silky smooth as we left via the downwind leg and headed north.

There was a thin layer of stratus at ground level which I skirted the thickest part and I chose to climb to 3500 to give us the best options should we have an engine failure (being forefront in my mind after the last flight). ATIS had forecast 50km visibility and it was roughly accurate, but once you get more than 20km vis it doesn't really matter at our modest speed.

There was a bit of traffic around Thames so we checked the VNC for the maximum altitude and started climbing to 4000 feet. There was some fair weather cumulus being blown in from the east so I climbed a little higher to 4300 to get above the base.

About 5 minutes after levelling off the engine started to surge. I knew instinctively it was probably carb icing but selected fuel pump on, then carb heat to hot. We held it for some time and the engine got worse as expected but did not seem to get better after about 2 minutes.

I did some mental maths. We were close enough to make Matarangi, Coromandel township, Whitianga or possibly Thames at our current position, even if we were forced to glide. If I continued north that list would be cut to Coromandel or Matarangi, and other alternatives like roads, beaches or somewhere in the mountainous and heavily forested Coromandel Penninsula.

View Larger Map

I chose to divert to Whitianga for two reasons, one, it had a long main runway, and two I had flown there before and was familiar with flying in that area. Our position was roughly 3nm from Whitianga, and I had a lot of altitude to lose, so I chose to remove distance from the equation and flew a shallow descent to the airfield and then descended in a spiral descent over the field until we reached joining height. I had performed a couple of engine warms during that time and the engine was fine till the throttle hit the end stop then it would surge and cough. When I leveled off at 1500 feet and performed an overhead join, at shallow throttle settings the engine was running fine and we were easily able to maintain altitude so I joined and landed without any fuss.

We taxied to the Mercury Bay clubrooms and shutdown. Chris rang up the Waikato Aero Club on his mobile and spoke with an instructor who counseled us on our options. They were pretty sure it was simple carb icing and had we climbed or descended it would have cleared in due course. They did ask me to check the fuel drains for water contamination, which thankfully was not the case. I wasn't 100% certain I wanted to continue onto the Barrier. The rough terrain, a trip across 5nm of open sea and a lack of suitable landing sites didn't instill me with much confidence. And we were also running out of time.

We chose instead to return to Hamilton, a trip I have flown about 3 times previously. Needless to say, the trip back was as normal as the trip over had been eventful. It was still an awesome day to go flying though, and I am simply glad I was up there. Chris took some photos with his array of different camera's so I am waiting to see the results appear on his site shortly.

{addendum} A day later in the nice warm Aero Club Bar on a chilly Sunday evening, Chris and I related our story to the clubs old timers. They rubbed their chins thoughtfully, nodded their heads together and said sounded like fuel contamination and not carb icing that was my problem. They reckoned I had a few small drops of water in one of the tanks (switching tanks didn't occur to me at the time but I'll try it next time) and that was what was causing the issue. One of the two off duty instructors present concurred with them. When I asked the instructor if one got carb icing how long should it take carb heat to remove the icing they replied no longer than 20 seconds or so. Since I had carb heat selected for a couple of minutes the pieces of this puzzle all seem to fit now. So remember to check and double check those fuel drains folks!


ZK-JPY said…
Perhaps you should plan a trip someplace else like Taupo?

It seems like you are not meant to fly to the Barrier... :(

Is there going to be a Take 3?... Third times a charm maybe?
Euan Kilgour said…
Chris said next time we are taking the Arrow and he'll fly. Trip is booked for sometime in mid June.

But I have flown to the Barrier before, on my long dual cross country. Here's hoping the third time is a charm.