1. Do the engines generally make it to TBO? (1800hours).
I have seen them go both ways. I few years back we had a fair bit of cylinder trouble with the blue seal A1 series and I know at least 4 cylinders on 1 engine had to be changed about half life within 300-400 hours of each.
Turbos seem to be more of a problem these days with much lower time pilots and with pilot turn over - more training etc.
2. What is the realistic gps groundspeeds and fuel flow do you see at 8500 feet?
170kts / about 140 l/hr in the cruse but as a block fuel flow for the entire flight Navajo 155 l/hr, Chieftain 165 l/hr. Can burn around 240 l/hr in the climb
I have seen quit a bit of difference in cruise FF between same engines models 18-24 GPH
3. Are the undercarriage as robust as an aztec?
Never flown the aztruck but have operated both Navajo's and Chieftain from grass, gravel and short strips without trouble. Problems with the micro switches is the main issue I have had with them - wheels not wanting to go up and not indicating 3 greens. Also there is a lot of difference between models with single and double calliper brakes!
If you want a machine with all the gear on it find a PA31-350-1020.
In my experience: (I'm not an owner)
- Navajo at MTOW performs better then a Chieftain at MTOW.
- Navajo's usually have 10-15 L more usable fuel and burn 10 L/hr less then Chieftains.
- Unless you are always flying long sectors make sure the PA31 has the undercarriage mod "Red Legs" otherwise you will be landing weight limited.