what_next wrote:
No aircraft would get certified and no pilot would pass his checkride if maintaining directional control upon uneven engine spool-up (or failure of an engine at any time – from commencement of takeoff roll to stopping after landing!) would be a problem
Maintaining control with one engine at full power and the other failed at, say, 20 kt, would require closing the other throttle and stopping. Below Vmcg (minimum control speed on the ground) you have to reduce the asymmetry, and Vmcg for an airliner can be 100-125 kt.
Once seen, never forgotten.
chrisparker wrote:
Maintaining control with one engine at full power and the other failed at, say, 20 kt, would require closing the other throttle and stopping.
Yes of course. But this should all be part of multi-engine and type rating instruction.
OutOfIInterest – Flying off dirt strips in Oz the recommended technique was to start engine and taxi all in one action, doing mag checks etc on the go and without hesitation take off. Some people found this difficult because they had been so inculcated to do all checks statically and hence the dirt being recirculated back into the engine – so definitely no holding against brakes! .
So I’m currently reading the book “Fly the Engine” by Thomas Kas, which I generally find interesting. He discusses a lot of the issues that we have had here, e.g. doing engine checks into the wind. Some of the advice comes “ex cathedra” without any real justification though, so you could say there is a good deal of personal opinion, but informed from real world flying and gathering of experience. But overall I like it since it makes for light reading and makes me revisit some things I had forgotten.
There is one issue though where I think he is wrong, or I’m just not bright enough. He advises against standing on the brakes before take-off unless you need every foot of the runway. I agree for two reasons, that are engine cooling and not blowing up dirt into your prop and onto the nosegear strut and O-rings. What I don’t understand is this:
Standing on the brakes at full power is stressful on the brakes, stressful on the propeller (the blades bend forward about an inch), and stressful on the engine’s thrust bearing, which is the area of the crank where thrust gets transferred to the rest of the engine (and thus the plane). The thrust bearing is large and can take the thrust, but you’ll be wearing it out faster if you stand on the brakes a lot.
The propeller and the thrust bearing can’t know what happens to the forces that are pulling on them – whether they will be transformed into some forward motion or just blowing back air. Doing a full power takeoff and climbout, the pulling forces will be about the same, and standing on the brakes for 2-5 seconds wouldn’t make much of a difference to the total time that an engine runs at this power.
aart wrote:
As an aside, static take-offs are great for getting debris into you props and for that reason alone I try to avoid them.
Agree. Once the rolling has started, full power will blow any dirt or debris back behind the prop and not suck it into the disc.
Also I think the passengers like the rolling take-off more, since it is smoother and less dramatic.
Interesting that the FAA has actually proved what many of us suspected – that it hardly matters for the take-off roll length. Except perhaps a bit for the turbo-charged.
