Selection of ground fine/discing on touchdown
 

I am interested to hear the pros and cons of the best time to select Disc or the equivalent engine-prop setting on touchdown (on a multi-engine aircraft). Should one wait until fully de-rotated with nosewheel contact in case of one prop failing to fine off beyond flight idle pitch or is there a certification standard ensuring sufficient control in yaw using aerodynamic forces?

sr

Not sure what type of machine you at referring to, but my experience on TP's, I would say it's not necessary to have the nose gear on the deck, since it's easy to counteract with rudder and brake in case there's a problem with prop pitch control, selecting full freverse is another story. :eek:

...and then there's the problem of the nosewheel arriving with a thud if the ground range is selected if the nosewheel is still airborne. This is because the ground range may (maybe even momentarily) destroy the elevator's authority. It is possible, but you have to give the column a huge great heave (Fokker 27 & 50).

PM

As an another example in the DHC-8-100 (exclude the Q400), typically (barring any gust or such) I would pull the throttles back in the flare, timing it to reach a point just above Flight Idle right before touchdown (leaving just a touch of power on to avoid the prop drag of the Flight Beta range and the resulting thump), flight idle as soon as the first main touches, and then SLOWLY "crack" the throttles about 1/4 of the way past the gate to Disc as soon as both mains are definitely on the ground. Then, SLOWLY bring it all the way back to Disc while allowing the nose to gently settle with steadily increasing yoke backpressure against the increased drag, basically pulling back on the wheel "in time" with the movement of throttle to touch the nose and the Disc stop at the same time. You can milk this out for quite a while and get an very smooth deceleration while avoiding the "skipping" bounces that Dashes sometimes do even with nice landings without using beta. In the earlier Dash the spoilers don't pop out until the nose gear is on the ground, so this sequence of beta usage provides an alternative lift killer to prevent the bounces while being gentle enough to prevent control issues. Of course you can do this more aggressively on a shorter runway; there is still plenty of elevator control left even if you go to full disc right after touchdown as long as the speed is reasonable and you have a halfway decent feel for the airplane. The Q400 is a whole different beast.

Superfine was only available on the Britannia when the nose leg was compressed.

In our Dash8 company SOP is lower nose wheel then apply disc. Reason given was instead of engine failure.

In our case there was no SOP regarding the timing of the use of disc per se; different pilots did it different ways, as did different instructors. Most did not wait for the nose to come down. Personal experience and a few thousand hours in the airplane later, it seems like the guys who put the nose down before starting to use Disc had faster and longer landing rollouts (for obvious reasons). This was always uncomfortable on some short runways and resulted in the one and only time in my career that I've ever had to physically take an aircraft from someone who was not a student.

Have never heard of anyone losing an engine in the Dash during that part of landing (not that it hasn't happened), and if the prop overspeeds in Disc one would imagine the nose would come down immediately whether you wanted it too or not. In assessing the comparative risks I'd go with the technique mentioned in the previous post, personally. Barring something limiting in the type's AFM / FCOM, it comes down to SOPs and technique, in that order.