General 737NG MCP Question

[Guest Tomlin]

This was noticed in many pictures a while back of real NG's, but now after flying the PMDG NG for dozens of flights, I have to ask:Why does the MCP SPD setting of 100 always come up as a default? Before my taxi, I have forced myself into the routine of setting it to 250IAS since I found out the hard way that not setting it to the desire speed will cause somthing that looks like this to come up on the readout- A100 after engaging the AP button upon reaching 1000 feet on climbout. Then of course if you dont watch it, the airspeed drops and you set off the stick shaker. Now, at first I thought since the FMC automatically sets the climbout speed to the speed restriction of 250 (sometimes 260 for some weird reason-why?) after engaging the AP button, that I would try leaving it at the default 100IAS. I dont do it anymore. Any reasons why it defaults to 100? (real world)

[Guest Erups]

>default? Before my taxi, I have forced myself into the routine>of setting it to 250IASTo follow exact procedure, you should set the V2 speed prior to takeoff.>since I found out the hard way that>not setting it to the desire speed will cause somthing that>looks like this to come up on the readout- A100It's something i call "alpha floor" from my airbus days: when you command a speed below the minimum sustain, you wil get the flashing A.Don't know for what it stands in boeings, in airbuses it is the alpha floor, hence my definition :)>Any reasons why it defaults to 100? (real world)Don't know :(

[kerke 0]

>To follow exact procedure, you should set the V2 speed prior>to takeoff.Aren't you supposed to set the speed to V2+10 instead of just V2? I believe the tutorial says to set the speed to V2+10 from the FMC calculated V2 value on the Takeoff page.On takeoff, when I activate the autopilot (AP1 button) at about 500-1000', the aircraft goes into LVL CHG mode and maintains the takeoff speed. Then at one point, when I hit LNAV at about 1500-3000', the smootly aircraft accelerates and climbs maintaining 250 on the speed to 10000.Best Regards from Miami/FloridaKerke

[Guest Tomlin]

Okay, so youre saying to:Set the MCP IAS to V2+10 After rotating and following the initial climbout following the flight director, the a/c always continues to gain speed. Are you suggesting that you pull the throttle back to maintain V2+10 until you engage the A/P?thanks,

[marcom 139]

Okay guys quite a few wrong concepts here!First of all, you don't set V2+10, you always set V2!Next: The A flashing in the MCP is not alpha floor. I don't know what it stands for, but it indicates "underspeed", i.e. you've selected a speed that is too low for the current phase. (i.e. below minimum selectable speed). You also get a flashing warning for overspeeds (try selecting 399 kts)Then, regarding the 200 kt default value: this is just a default power up value and has no operational meaning at all, well not quite true as it indicates that it is operational ;-). Same as 10000 ft in the Alt box and 000 on the heading.Regading alpha floor: this option also exists on the 737 - the AP won't allow you to stall. The A/T will command a higher thrust if you get too close to stall speed. This is similar to the Airbus concept, but there you have no option of overriding it. On the 737 you can still disconnect the AP and disengage the A/T if you really want to hear the stick shaker :-)

[Mats_J 2]

Eric,>Any reasons why it defaults to 100? (real world)Actually I think it defaults to 110 in the real world out there. DOn't have a clue why though. Nice and round figure?

[Guest Erups]

>Okay, so youre saying to:>>Set the MCP IAS to V2+10 >>After rotating and following the initial climbout following>the flight director, the a/c always continues to gain speed.>Are you suggesting that you pull the throttle back to maintain>V2+10 until you engage the A/P?Read the manual please, it is clear on this.You are required to complete the PRE FLIGHT checklists, and set V2 on the mcp.Then engage TOGA mode (eighter with A/T connected or not), and follow the FD bars: they will command pitch in order to maintain V2+20 until you change to another vertical mode and change speed.

[kerke 0]

>Okay guys quite a few wrong concepts here!>>First of all, you don't set V2+10, you always set V2!I completely believe you, but here's a quote from the PMDG Flight Tutorial:---------------------------------Takeoff PreparationYou will need to prepare your cockpit for takeoff.

[Guest Erups]

>Next: The A flashing in the MCP is not alpha floor. I know, and told it was not so.But i, just as you, don't know what it stands for.Anyway it's an A/T protection in case of errors on the input by the pilot.

[Guest Tomlin]

>Read the manual please, it is clear on this.>You are required to complete the PRE FLIGHT checklists, and>set V2 on the mcp.>Then engage TOGA mode (eighter with A/T connected or not), and>follow the FD bars: they will command pitch in order to>maintain V2+20 until you change to another vertical mode and>change speed.Claudio-My original question was simply why when the a/c's electrical system is powered up does it default to 100. The simple answer is that it's the default, that's it, nothing more or less. My 2nd question was basically taken and ran with simply because I indicated that I put a value in for the IAS somthing higher than 100 to be safe, and the aircraft's FMC will always automatically put in either 250 or 260 on the IAS for the climb when A/P is engaged. It's not clear to me how V2 is maintained at all until you engage the A/P button. That's why I asked in the first place. But again, the first question was simply "why does it default to 100?". Now we know- that is just where it's programmed to default to.BTW, See: http://www.airliners.net/open.file/295361/L/Thanks all!Eric T

[marcom 139]

Hi Kerke,in that case the writer of the tutorial made a small mistake.Again, only V2 without any additives in any conditions is set in the MCP Speed Window.Regarding the quote from the normal procedures manual:it doesn't say that you should set V2+15, but that you should maintain it! The FD will automatically do that (it basically adds the 15 knots to the entered V2 speed)You can observe this by selecting for example SPD after takeoff. Note how the speed window "jumps".Regards,Mark

[crvm 0]

why when the a/c's electrical system is powered up does it default to 100. It's because the real 737 NG MCP defaults to 100 on power up. I do belive the Classic defaults to 110.My 2nd question was basically taken and ran with simply because I indicated that I put a value in for the IAS somthing higher than 100 to be safe, and the aircraft's FMC will always automatically put in either 250 or 260 on the IAS for the climb when A/P is engaged. It's not clear to me how V2 is maintained at all until you engage the A/P button. You set V2 into the window, the AFDS automatically displays flight director guidence for V2 PLUS 20 than you manually follow, not the A/P. That's why it is not clear because it's not done by auto. FLight director guidence with F/D on and TOGA engaged. http://forums.avsim.net/user_files/95146.jpg And Mark is correct, that was a mistake and has been mentioned many times on this forum most by me ;-)Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/Animation1.gifCaution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | NEC LCD 1980SXi 19" | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro |

[Balint 18]

Mats,"Nice and round figure?"I guess other than that it is also a value that you will either way have to set to a different one, making sure you will never forget to deal with this. Backup's backup. Makes sense to me after all the precaution-wise compiled systems we have on the NG..Cheers,

[Guest captbulldog 2]

A = ABOVE -- as in you're flying ABOVE your set speed in MCP