Stick Pushers
 

I have heard some conflicting reports on the reasons why some manufacturers choose to outfit their aircraft with stick pushers. I am aware that some aircraft have pushers while others don't. Does anyone have background information as to the certification process, and/or requirements that mandate some aircraft to have them (Gulfstream) while others do not (Falcons)? I'm curious to hear your thoughts on this subject, and specifically, if an aircraft has a stick pusher, does that mean it has an inherant design flaw if allowed to approach a deep stall condition? Thanks in advance.

Falcons dont stall.

I certainly wouldn't say "design flaw"....swept-wing jets don't tend to aerodynamically react well to a wing stall, and my guess is how a particular wing & aircraft behave in full stall is how some end up with pushers while others do not.

My understanding is that with Transport Category aircraft with T-tails require a stick pusher due to the possibility to enter "deep stall conditions."

When they put delta fins on the 55C which morphed into the LR60 they realized that the deltas helped to pitch the nose down and they took out the stick pusher. They also took away one yaw damp and allow us to dispatch without it at all, unlike the LR series.

Can't comment on other T-tails

Fly By Wire and stop worrying about that 1980 crap.

:)

Yea... hey, just engage the autopilot and forget about it. Good answer :rolleyes: Or pretend you're flying and the wire is not there... hmmm.... good ol days when we used to fly.... back in the crap 80's...

Who said anything about Autopilots?

I hand fly a brand new FBW plane far more than I ever flew a 1980s POS
Learjet....

Note the smiley face and get off my lawn Pops!!! - lighten up or Santas gonna bring you coal.

Hehehe....no wait, I fly a 900 too :o

well you're right. no more egg nog for me. merry xmas.

Seven Two Sevens and baby Nines don't have pushers. MD-80s got them after Douglas had to pop the shute during stall testing.

Well this is not the case, as I fly a tranport category aircraft with a T-tail and no stick pusher.

What do you fly?

To Push the Stick
 

It is my understanding that during development if it is found that the aircraft has certain "undesirable" characteristics (may require exceptional skill) from the pre stall buffet (if any) through the stall break (if any, Controls may reach the aft pitch stop) that a stall recognition system can be installed. These would include big red signs, stick shakers and stick pushers.
The undesirable characteristics would be a roll exceeding 20° (wings level stall). The stall itself cannot be violent or extreme or needing anything but "normal piloting skill". A stick force per 'g' reversal or a reduction in stick force is usually a no no.
So they can add say a stick shaker if there is little aerodynamic warning and a stick pusher to really prevent the stall and send the message to the pilot that a recovery should be initiated when the actual stall will be "exciting". Delta fins usually are used to during power on (1.5 time the power to maintain level flight with landing gear extended and flaps at approach setting Vsr1) stalls where there is not a clean enough break or sufficient downward pitching moment through the stall.

AC 25-7B
FAR 25 Subpart B - Flight

Stick pushers were a compromise. When psychologists discovered that the current generation of pilots was too rebellious to obey stall warnings, a head-knocker was designed, but OSHA vetoed that as too cruel. The banana reward-dispenser was too slow, and invited a secondary stall while the pilot ate. The throttle auto-firewall system caused too many unwanted go-arounds. Designers just ran out of good ideas. :D

For whatever reason, the Dash 8-300/400 series has a pusher, while the -200/100 does not.

Something "undesirable" must have happened during -300 certification.

And I hand flew my 1960's Sabreliner at FL410 with the yaw damper off, something you couldn't do in a POS Learjet either! And I didn't have to sit with my head tilted to one side! :D

Some FBW aircraft do not have them because the elevator will pitch down, regardless of column/sidestick input, in the event the aircraft approaches the critical angle of attack.

How's that working for Airbus?

I fly a lr60 and it does not have a stick pusher. The lear 35A had a stick pusher

I've flown the EMB-145 which had a pusher... probably a good thing because when we messed around in the sim, it would take an incredible amount of altitude to recover from a stall.

The BE400 doesn't have a pusher, but it also recovers pretty quickly on a stall.

The Falcon 900 stall protection includes auto slat extension that creates a pitch down force. IIRC, this met the certification requirements without the need for a pusher.

My understanding was that pushers were installed on aircraft with artificial feel units in the system. The issue was not being able to recognise the deepening of a stall by feel because of the synthetic feedback from the aircraft. Then again I flew the POS EMB-145 and it had a pusher even though the elevator was not hydraulically boosted. Odd for a 50k airplane...

It is my understanding that a plane gets a shaker if the wing does not give sufficient buffet to feel the stall, and a pusher if the plane is difficult to recover from a stall. Wings designed for high Mach numbers generally have airfoils that don't give much buffet close to stall, and have lots of sweep which make it hard or impossible to get the nose down in a stall. A T tail can make this worse, but does not necessarily require a shaker. Look at the CJ's. They have a t tail, but not much sweep, and a more forgiving airfoil. No pusher is required because it will come out of a stall easily.

If the french can do it, it can't be that hard.:rolleyes: