blackbird7

Question on Chuck's Maddog X P3D Tutorial

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Hi all,

I am learning the ins and outs of the Maddog X and am really enjoying the experience. I am following Chuck's Leonardo P3D MD-82 Guide to learn the different phases of flight. I seem to be able to understand/apply all of the steps up until the SET UP APPROACH phase and am wondering if I am doing something wrong or missing a step somewhere:

 

The guide states on p. 147:

16. Set SPD knob to 170 kts (FOWLE speed limit). Orange speed command bug will be set as well.

17. Once aircraft has slowed down to 170 kts, set flaps lever to 0 deg.

 

However, setting the SPD knob to 170 kts doesn't slow down the Maddog, even with landing gear deployed.  The orange speed command bug does say 170 kts, and the FMA displays "ALFA SPD". So, I had a few thoughts on what I should be doing to slow the aircraft down:

1. Should I be lowering the flaps lever to 0 deg to slow the aircraft down to 170 kts instead of waiting for the aircraft to slow down on its own? 

2. Should I extend the speed brake to get to 170 kts, then deploy the flaps lever to 0 deg?

3. Or do I need to further configure the autopilot, perhaps hitting the SPD button on the FGCP to enable the SPEED Autothrottle Mode button?

 

Do any of these methods sound right? Any suggestions would be greatly appreciated. 🙂

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Make sure to hit the Fmc speed override button. Also make sure your throttle is in the idle position. The plane is not very slippery and should slow down on its own. I don’t think I’ve ever needed to deploy speed brakes. Also how are you descending? Usually I use v/s mode and can control speed fairly easily by monitoring my descent rate.

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I have read the guide. And Chuck has incorrectly stated that at the given weight, max speed for Slat extended to MID pos is 179 knots IAS. This is actually the minimum manoevering speed (Vman). So it' s natural that the aircraft will warn for alfa speed when you set speed to 170.

For the MD80, slats can be deployed at quite high speeds (compared to the A320 for example) so don't be afraid to capture the glideslope with slats fully extended and flaps 15. Then go gear down and flaps 28 / 40.

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Posted (edited)
1 hour ago, blackbird7 said:

Hi all,

I am learning the ins and outs of the Maddog X and am really enjoying the experience. I am following Chuck's Leonardo P3D MD-82 Guide to learn the different phases of flight. I seem to be able to understand/apply all of the steps up until the SET UP APPROACH phase and am wondering if I am doing something wrong or missing a step somewhere:

 

The guide states on p. 147:

16. Set SPD knob to 170 kts (FOWLE speed limit). Orange speed command bug will be set as well.

17. Once aircraft has slowed down to 170 kts, set flaps lever to 0 deg.

 

However, setting the SPD knob to 170 kts doesn't slow down the Maddog, even with landing gear deployed.  The orange speed command bug does say 170 kts, and the FMA displays "ALFA SPD". So, I had a few thoughts on what I should be doing to slow the aircraft down:

1. Should I be lowering the flaps lever to 0 deg to slow the aircraft down to 170 kts instead of waiting for the aircraft to slow down on its own? 

2. Should I extend the speed brake to get to 170 kts, then deploy the flaps lever to 0 deg?

3. Or do I need to further configure the autopilot, perhaps hitting the SPD button on the FGCP to enable the SPEED Autothrottle Mode button?

 

Do any of these methods sound right? Any suggestions would be greatly appreciated. 🙂

I wanted to ensure that what you experienced was normal, it's essentially a "save speed" type function where the autothrottle will not allow the aircraft to slow less than the safe minimum airspeed for the existing configuration (slats and flaps).  It's a safery feature built into the avionics.  To continue to slow, past approximately 210 knots, simply extend the slats and then pay attention to the save maneuvering speed and set the flaps as calculated by the DFGS (displayed in the CDU and the Indicated Airspeed gauge) or use the provided tables.

I hope this helps answer your question.

 

Best wishes!

 

Edited by DaveCT2003
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3 hours ago, SAS443 said:

I have read the guide. And Chuck has incorrectly stated that at the given weight, max speed for Slat extended to MID pos is 179 knots IAS. This is actually the minimum manoevering speed (Vman). So it' s natural that the aircraft will warn for alfa speed when you set speed to 170.

For the MD80, slats can be deployed at quite high speeds (compared to the A320 for example) so don't be afraid to capture the glideslope with slats fully extended and flaps 15. Then go gear down and flaps 28 / 40.

 

3 hours ago, DaveCT2003 said:

I wanted to ensure that what you experienced was normal, it's essentially a "save speed" type function where the autothrottle will not allow the aircraft to slow less than the safe minimum airspeed for the existing configuration (slats and flaps).  It's a safery feature built into the avionics.  To continue to slow, past approximately 210 knots, simply extend the slats and then pay attention to the save maneuvering speed and set the flaps as calculated by the DFGS (displayed in the CDU and the Indicated Airspeed gauge) or use the provided tables.

I hope this helps answer your question.

 

Best wishes!

 

Thanks guys for these responses.  I was a bit baffled trying to figure out what I was doing wrong or what I should be doing instead. Your explanations make a lot of sense and will help with the next flight. Thanks again!

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Posted (edited)

The Vman speeds in the table on the top right of the page are the minimum maneuvering speeds for that flap/slat setting.

From the fcom:

"If autothrottles are engaged, the autothrottle system (ATS) will reference to alpha floor (1.3 VS in landing configuration) or speed selected with the airspeed command bug, whichever is greater."

So if you're getting the ALFA speed it means you're trying to go below minimum safe speed.

Also the maximum speeds for extension are quite high as mentioned above.

VFE speeds:

0º - 13º  280 kts

15º - 20º   240 kts

21º - 25º  220 kts

26º - 27º  200 kts / 205 kts MD83

28º - 40º  195 kts / 200 kts MD83

Edited by itsjase

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