Second flight of BFR

[cjsmith]

Stalls: WAY better than last week
Landings: WAY better than last week (I think I get to log only one per arrival this time)

My instructor also pulled the power on me when we were over the coast, which I'll happily take as another indication that I'm getting better. Now I need to chair-fly a few things: a standard pattern, the division of attention between sight picture and airspeed indicator on final, and the engine-out fuel flow check.

The most interesting bit happened before we took off, though. I got a stunning demonstration of why, if you're going to test both fuel tanks on the ground, you switch tanks early -- not right before run-up. My instructor had me turn the fuel selector switch to OFF, then do my engine run-up, check the mags and carb heat, check the controls, etc., and after that, over the continuing engine noise (!!) we chatted in the cockpit simulating the "you are cleared for takeoff" exchange with tower. The engine finally quit due to fuel starvation when we would have been a few hundred feet in the air. Badness 10000.

Comments

[datagoddess.livejournal.com]

I'm confused.

I understand turning the switch to off, and that the engine kept running for awhile. I'm assuming that meant that it wasn't pulling from either tank.

I don't understand why you would do that, and what is meant by testing the fuel tanks and switching tanks early. I are ignorant on flying stuff.

:-)

[cjsmith.livejournal.com]

Right, the engine was pulling from the fuel lines and it took that long for those lines to run dry.

I would do that only as a demo. I've never done it before. This showed me how long it takes after you turn the tank selector switch OFF for the engine to finally die. It was a much longer time than I thought.

Testing 'em: Usually the checklists for my type of aircraft (low wing, two separate fuel tanks, one in each wing) say: "Set the switch to one tank, talk to ground control and taxi over to the runway, now you know that tank works and has fuel in it, switch to the OTHER one, run the engine up to 2000 rpm and do some checks, now take off." This is done in an attempt to make sure fuel is feeding properly from both tanks before you get into the air.

The demo showed me that with this procedure if your *second* tank was bone-dry (or had something wedged in the fuel line where it meets the tank) you'll have an engine failure shortly after takeoff... not, as most pilots suspect, while you're still on the ground. Shortly after takeoff is the worst time ever. This safety procedure is therefore potentially harmful instead of helpful! So the idea is: if you're going to switch, switch before you taxi, leaving yourself as much time as possible for the engine to tell you something's wrong. (O'course that means less time for the engine to tell you something's wrong with the *first* tank. I'm going to ask Benjamin about this next time.)

[datagoddess.livejournal.com]

*lightbulb*

Thanks for the explaination :-)

[sunnydale47.livejournal.com]

"Nothing is as useless as the altitude above you, the runway behind you, or the fuel at the airport!"