GA1313

I’m a (300+hrs) PPL holder and fly frequently with other pilots and passengers. On a bright breezy summer’s day, myself as P1 and three non-pilot passengers flew in a PA28 180HP Archer uneventfully to [Airfield] and spent a very enjoyable time there. Late afternoon we got back in for the return flight. I’d checked the fuel, weather and my moving map was all set. All was well and we now had an 18Kt wind straight down the runway for take-off which, as a tailwind, would push us home faster.

I always use my Pooleys PA28 checklist and, taking my time, did so as we started up, did power checks and pre-take-off checks. We were then cleared to line up and take off. Being a [long] runway and entering at the [xx] hold, which is about half-length, I had checked and knew we had more than sufficient to get airborne safely. Having lined up, stopped to check the DI and my moving map were all correct, I applied full power and we began the take-off roll. A quick gauge check and I noticed the RPM was about 100 below what I expected but we were accelerating rapidly and into the brisk wind were soon airborne and commencing a right turn climb out. I then noted that our rate of climb was 400/500FPM not the usual 700FPM.

Saying to myself (passengers enjoying the view and oblivious anything was other than normal) this is not a crisis but something isn’t right I duly checked mixture fully rich, flaps up, fuel pressure & oil pressure in the green, carb heat cold but cycled with RPM drop & recovery. I decided to continue the climb to 2000’ then level off and make a left orbit to the north of the field as I didn’t want to get too far away if I did have an engine problem. I would then take another look at the situation. I considered it to be a situation that was not an emergency because the engine was smoothly producing power and all indications were normal though a bit low on RPM. I elected not to advise ATC at this stage as was now clear of the ATZ on the Approach frequency with a Basic Service. Level, and ensuring primarily I flew the aircraft and about to commence the LH orbit, I went through all the key checks:

• Mixture rich
• Change tanks fuel pressure good – no change in RPM
• Oil pressure & Temp both nicely in the green
• Carb heat cycled with RPM drop & recovery but still low.
• Alternator online and charging
• And finally Mags on ‘both’ only to find that the key was set to only one Mag not both. Turned to both and the RPM instantly increased as did the rate of climb to 700FPM.

We then continued on course for a pleasant uneventful flight home. The checklist states “Magnetos – on Both, check master on” but I had somehow left the switch on one magneto not both. Back on the ground at home base I checked the switch carefully, it wasn’t loose and positively clicked to each position for each mag and both so not at fault. The situation was of my making. The degraded engine performance had a degree of risk by reducing the climb rate but as we weren’t flying towards high ground and were climbing I consider it in the low category, however had the selected mag failed it could very quickly have become a full blown emergency which, with a little more diligence on my part, I could have and should have avoided. Lesson learned.