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Why 100 Kts IAS On This 737 Autopilot?  
User currently offlineJgore From Argentina, joined Feb 2002, 550 posts, RR: 2
Posted (11 years 9 months 3 weeks 2 days 1 hour ago) and read 3766 times:

Hi

Please take a look at this picture.


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Photo © Joe Corrigan



Why would pilots set 100 kts ias in their autopilot since they land or takeoff about 130-145 kts ?.
Is this somehow useful in any phase of flight ?  Confused

Thanks in advance

Regards

Jgore  Smile

12 replies: All unread, jump to last
 
User currently offlineT prop From United States of America, joined Apr 2001, 1029 posts, RR: 1
Reply 1, posted (11 years 9 months 3 weeks 1 day 23 hours ago) and read 3700 times:

The airplane is on the ground with both engines shut off, I imagine the autopliot is not needed in this situation.

T prop.


User currently offlineCdfMxTech From United States of America, joined Jul 2000, 1341 posts, RR: 26
Reply 2, posted (11 years 9 months 3 weeks 1 day 23 hours ago) and read 3696 times:

First of all, if those guys are inflight, they are in major trouble!! Big thumbs up
That flightdeck is not prepared for flight.They are on the ground and nothing is setup.

Anyway, inflight the mode control panel would not let you set a speed below the alpha floor limit. I think it is something like 1.3 times the stall speed.


User currently offlineJgore From Argentina, joined Feb 2002, 550 posts, RR: 2
Reply 3, posted (11 years 9 months 3 weeks 1 day 22 hours ago) and read 3668 times:

Well, I know is not necesary when the airplane is grouded. But I doubt pilots or any mantenience guy were playing with the knob leaving the counter in 100.

Jgore  Smile


User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 4, posted (11 years 9 months 3 weeks 1 day 20 hours ago) and read 3648 times:

It's most likely a default value.At least that's how it reads on our MD-80/90 readouts when a powerchange has occurred and no pilot-selected value has been entered.
You may well set 100 kts in the readout window during flight,however,the Flight Management System will prevent the plane from decellerating below Alpha (min speed for present configuration) and the Flight Management Annunciator will show ALFA SPD and control speed to applicable value.
But things can (will) go wrong,and no pilot in their right mind would set such a low speed in the readout.



"Luck and superstition wins all the time"!
User currently offlineCdfMxTech From United States of America, joined Jul 2000, 1341 posts, RR: 26
Reply 5, posted (11 years 9 months 3 weeks 1 day 19 hours ago) and read 3634 times:

But I doubt pilots or any mantenience guy were playing with the knob leaving the counter in 100.

FBU is correct. That is the default value on the IAS/MACH window when pwr is applied


User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 6, posted (11 years 9 months 3 weeks 1 day 17 hours ago) and read 3610 times:

Although it is probably not the case here, as evidenced by the well informed posts above, there is always the possibility that one of the segments on the speed display is burnt out. In other words, maybe 180 is set but 100 is displayed because the center segment of the "8" is missing.

User currently offlineAAR90 From United States of America, joined Jan 2000, 3474 posts, RR: 46
Reply 7, posted (11 years 9 months 3 weeks 1 day 17 hours ago) and read 3616 times:

I suspect the -700 has the same MCP as the -800.
From my AA 737-800 OpMan:
"IAS/MACH Display... Displays 100 knots when power is first applied."



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineGE From Singapore, joined Mar 2000, 320 posts, RR: 6
Reply 8, posted (11 years 9 months 3 weeks 1 day 16 hours ago) and read 3606 times:

It's the same for the A319/320/321.
100 knots is displayed on the Flight Control Unit when first powered up.

Regards,
Russell J.


User currently offlineJgore From Argentina, joined Feb 2002, 550 posts, RR: 2
Reply 9, posted (11 years 9 months 3 weeks 1 day 13 hours ago) and read 3562 times:

Ohhhh guys, you've made it very clear enough. Thank you very much.

Jgore  Smile


User currently offlineRick767 From United Kingdom, joined Jan 2000, 2662 posts, RR: 51
Reply 10, posted (11 years 9 months 3 weeks 23 hours ago) and read 3494 times:

Just to confirm, 100 knots is the minimum "default" value which appears in the 757/767 MCP Speed Window as well when the juice starts flowing.


I used to love the smell of Jet-A in the morning...
User currently offlineCx flyboy From Hong Kong, joined Dec 1999, 6601 posts, RR: 55
Reply 11, posted (11 years 9 months 3 weeks 10 hours ago) and read 3445 times:

Not quite related, but after landing, we always set the parking bay number as a reminder in the altitude window, so if bay 1 we set 100. Bay 10 we set 1000. It not a company requirement and it not written anywhere, but more something that we just do! just a reminder as sometimes the taxying can be complicated at some airports so you don't want to forget the bay number!

User currently offlineWardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 12, posted (11 years 9 months 2 weeks 4 days 13 hours ago) and read 3315 times:

Well take a look. The PFD display is almost displayed in black, meaning that they have just turned on the APU system. Like on the MD-11, when everything is first set up, the autopilot console will automatically will show a reading of the standard IAS as 250 knots. Or it could just be in a test mode. But again on the MD-11, it will say as "Fail" on the PFD.

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