View Full Version : PW121 Turbo prop(Beta)
I am just about to start training on a Dash8. Hence the question. Could somebody please explain the difference and the significance of the Beta Lockout & the Beta Backup.
AerocatS2A
2nd Dec 2013, 07:27
2nd Edit: I've had a look at the manual. It's not in my rather dated copy of the FCOM but it is in my sample copy of a flight manual. The basic beta backup that was originally installed on Dash 8s prevented the props from going into ground beta while airborne if the power levers were in the flight range. In other words they prevented ground beta caused by a system malfunction but the pilot could still select ground beta themselves and nothing would prevent it.
The beta lockout (BLS) is a mod (CR 873CH00011 for what it is worth) that has a warning horn (chirping birds) that sound if you lift the flight idle gate levers and revised beta backup system that allows the beta backup to prevent the props from going to ground beta even if the pilot has selected the power levers to the ground range. So it prevents the pilot from doing something stupid. The BLS is disabled on the ground and below 50' RADALT. The birds will chirp down to 20' RADALT.
The original beta backup is still functional on Dash 8s with beta lockout when the power levers are in the flight range.
I hope that's a bit more clear than my first answer.
P.S. If you've been given a copy of the flight manual, have a look in the Operating Data Manual, Chapter 21.20, page 7 or thereabouts. It will explain beta backup and may have a change bar with information on the lockout system.
Aerocat appreciate your response. Could you please elaborate on why there is an ECU switch Test and a ECU Valve Test.
AerocatS2A
2nd Dec 2013, 21:22
It's been a few years and that's not ringing any bells. What do you know about them so far?
It could be something specific to the PW121. I only flew the 200 and 300 series Dash 8 which have the PW123.
tmpffisch
17th Dec 2013, 07:50
Absolutely correct. The ATSB worked very hard to make a Beta Lockout system a mandatory modification; which was eventually done...only Bombardier provided a 5 year rollout window for operators to get it done. (considered to be a "kick in the gut")
After sitting through an ATSB conference on this very issue, it takes about 2-3 seconds of an inadvertent activation of beta to cause catastrophic destruction of the engine.