Stick Pushers
#11
Seven Two Sevens and baby Nines don't have pushers. MD-80s got them after Douglas had to pop the shute during stall testing.
#12
Gets Weekends Off
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#14
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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.
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.
#15
Gets Weekends Off
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From: G550 & CL300 PIC
Originally Posted by AC25-7B Chapter 8 Paragraph 228 - Design and Function of Artificial Stall Warning and Identification Systems.
Some airplanes require artificial stall warning systems, such as stick shakers, to compensate for a lack of clearly identifiable natural stall warning to show compliance with the stall warning requirements of § 25.207. Similarly, some airplanes require a stall identification device or system (e.g., stick pusher, automatic inboard slat segment retraction, auto-trim, etc.) to compensate for an inability to meet the stalling definitions of § 25.201 or the stall characteristics requirements of § 25.203.
FAR 25 Subpart B - Flight
#16
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.
#18
Eats shoots and leaves...
Joined: Apr 2007
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From: Didactic Synthetic Aviation Experience Provider
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