Is a 152 used for scheduled 135 cargo operations at 170 knots usually at night and in marginal weather, operated single pilot IFR and equipped with 4-6 fuel tanks supplying two turbocharged engines?

 

That's a lot of stipulations. You didn't specify that in your original statement. Cessna 310s meet those specifications and don't have lights or anything. Is there any pistons that do?

 

Trying to remember, wasn't there an issue in the PA31 (or the twin Cessnas maybe?) with the fuel selector rigging? The selector goes all the way but the valve gets stuck on either the first tank or in between (effectively off)?

 

I know this was an issue in the Cessna 402. You have to keep an eye on your fuel tanks if you switch them.

 

This really isn't an ego thing. It works on a really simple principle that you engineers tend to forget sometimes: KISS.

The Navajo has three ways of telling you:
Fuel selector handle
Fuel pressure guage
Low Fuel Press Lights

Number one is really not rocket science. Flip the handle, look down. Done. That's your indicator. It's even labeled.

If you manage to screw up all three it really will get your attention, but since the engine doesn't really quit running just get the selector in the right place and hit the boost pumps. 999 times out of thousand, problem solved.

I know you're flying Caravans now, and yes, the Caravan will very loudly yell at you if you turn off both tanks, but at the same time relighting a turbine engine is a very different thing.

 

I figured it'd be very quiet.

 

Yes, and that's what I was trying to get across until the ego contest got going again.

~~~

Best of luck to the Key Lime pilots in these hard times.

 

Naw, VERY loud warning horn. Each wing tank flows into a feeder tank (12 gallons if I recall?) and has an on/off valve to balance them. If your manage to turn both of them off with power to the airplane you get a loud horn, as a PT-6 burning 400 lbs/hour goes through the feeder tank pretty quick. And like I mentioned earlier, restarting a turbine is a complete different animal.
It's really not an ego contest. It's more like common sense if you think about it.

Switch tanks, then look at the selector. Works good, last long time. If the engine has a hiccup, look at the fuel selector. Been there done that. Guess what, I lived.

Adding some collection of microswitches and indicators is just something else that can break, and on the Navajo is entirely unnecessary.

 

Cubdriver is right. I have a background in human factors engineering. Many of the systems in planes like and older Seneca and Navajo are simply terrible. There's literally no chance in hell something like that could get certified today. Although humans are amazing at some things, they are poor machines and poor at doing things repetitively or correctly time and time again. If something is required for a safe outcome, this means that a small percentage of the time, it won't happen correctly and there will be an unsafe outcome. I'm very familiar with the PA-31. If the system was designed better, could the outcome have been avoided? Good chance yes. Was it still pilot error in that if the pilot performed perfectly it could have been avoided? Most likely. Is it reasonable to expect a human operating that system to operate it correctly every time? Probably not. I know 737 captains who keep their finger on the crossfeed pump the entire time they are crossfeeding, because they don't want to forget about it and because it has happened in the past. Why has it happened in the past? Systems like that are designed without adequate protections for human factors.

Good comparison is the GA-8 airvan design. It's a single engine, but looking at the problem of fuel balance, it's an absolutely ingenious solution, instead of having the right tank feed the right side of the reservoir, it feeds the opposite side, and it's designed to take fuel from whichever wing is lower/heavier, thereby it continually keeps feeding from the "heavy" wing, with no ability to select left or right, just a steady flow of fuel. It's designs like that which should be incorporated in aircraft design, still requiring you to track fuel burn, just not perform some unrealistic 4-tank or more management and try to guess when each tank is reaching it's end or other monkey magic.

None of these systems are likely too hard to overcome if you have all the time in the world and blue skies, but you start stacking tasks on top of each other and you start to get close to a point where something will break, which is more likely in many of these late model piston aircraft. There seems to be a point at which they went kind of crazy from relatively simple and few systems to far more complex and numerous systems, to add more features and capability. Now certification rules and standards are higher and many of these issues are designed out of the system in new aircraft.

 

When you talk about fuel tank design you can't compare a high wing aircraft to a low wing aircraft. The high wing aircraft is always going to be far easier to design and certify.