A320 Ferry flight with gear down
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A320 Ferry flight with gear down
Heya guys.
In the FCOM there is a procedure for special operation flight with the gear down.
It says about the switch on 188VU in the avionics bay to change the VMO to 235knots (from standard 280kt VLE).
This is fair enough because on a ferry flight there is a long time with the gear down so this reduction in VMO is to reduce fatigue.
My question is regarding the protections. Does this switch modify the protections so that the overspeed protection kicks in around 240? or does the barbers pole show 235kt but the overspeed remains at 280kt (VLE gear down)?
In the FCOM there is a procedure for special operation flight with the gear down.
It says about the switch on 188VU in the avionics bay to change the VMO to 235knots (from standard 280kt VLE).
This is fair enough because on a ferry flight there is a long time with the gear down so this reduction in VMO is to reduce fatigue.
My question is regarding the protections. Does this switch modify the protections so that the overspeed protection kicks in around 240? or does the barbers pole show 235kt but the overspeed remains at 280kt (VLE gear down)?
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Hello
Interesting question to which I was unable to find a written answer.
However, if you have a look at FCOM/PRO/SPO/25/30 ABN AND EMER PROCEDURES regarding dispatch with gear down, you will see that in case of a dual eng. failure you have to increase your speed up to 300 Kt to attempt a restart and it also says that you will have to disregard the VMO warning.
In normal conditions with the VMO/MMO switch set to "L/G DOWN", a VMO warning is only provided if 235 Kts are exceeded, I don't believe that it reduces the protection margins as well.
The bottom of the Barber Pole is computed by the FAC according to the airplane slat/flap configuration. The VMO/MMO speed computations done by the FAC do not take into account the landing gear position, however, an overspeed warning is probably available.
Standing to be corrected
Cheers
Interesting question to which I was unable to find a written answer.
However, if you have a look at FCOM/PRO/SPO/25/30 ABN AND EMER PROCEDURES regarding dispatch with gear down, you will see that in case of a dual eng. failure you have to increase your speed up to 300 Kt to attempt a restart and it also says that you will have to disregard the VMO warning.
In normal conditions with the VMO/MMO switch set to "L/G DOWN", a VMO warning is only provided if 235 Kts are exceeded, I don't believe that it reduces the protection margins as well.
The bottom of the Barber Pole is computed by the FAC according to the airplane slat/flap configuration. The VMO/MMO speed computations done by the FAC do not take into account the landing gear position, however, an overspeed warning is probably available.
Standing to be corrected
Cheers
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Haha, this would be a good starting point, however I suspect their situational awareness probably wasn't quite up the level required to notice what the overspeed was in knots/Mach.
I did see that note regarding the dual engine failure. This makes me think that the overspeed remains at 280 with the protections unmodified. So on the screen 235 will be the barbers pole but you could fly up to 280.
The aircraft does actually adjust the overspeed to 280kt with the gear down but you would very rarely see this as you usually have flap out by the time the gear comes down, and of course VFE is more limiting.
I did this in the sim while clean and then lowered the gear. The barbers pole came down to 280kts.
I did see that note regarding the dual engine failure. This makes me think that the overspeed remains at 280 with the protections unmodified. So on the screen 235 will be the barbers pole but you could fly up to 280.
The aircraft does actually adjust the overspeed to 280kt with the gear down but you would very rarely see this as you usually have flap out by the time the gear comes down, and of course VFE is more limiting.
I did this in the sim while clean and then lowered the gear. The barbers pole came down to 280kts.
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Applecrumble, did you manage to lower the gear above 250Kts in the sim ?
I tried the same and I had gear remaining in the retracted position with 3 reds ... Never checked where was the barber pole after gear extension ... might have a look at that during the next sim or sector. Any additional info on the subject is welcome.
I tried the same and I had gear remaining in the retracted position with 3 reds ... Never checked where was the barber pole after gear extension ... might have a look at that during the next sim or sector. Any additional info on the subject is welcome.
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At 260kts the safety valve cuts of hydraulic supply to landing gear so it won't come down. The protections only come in at VMO/MMO and not at VLE or VFE. So in my opinion only the VLE is amended.
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I agree I think that just the VLE is amended.
Last edited by applecrumble; 25th Aug 2017 at 15:10.
Only half a speed-brake
Vilas, could you verify that, pls?
I had a feeling that barber pole would come down the speed strip with the configuration (Vfe, Vle), however the overspeed protection stays as 350/.81 +6kt.
My review of FCOM SYS yesterday does not support that opinion, it seems to imply that red barber is the "Vmo of the moment" and overspeed protection is associated with it (green ticks). More research required, but maybe you already know how it actually is.
I had a feeling that barber pole would come down the speed strip with the configuration (Vfe, Vle), however the overspeed protection stays as 350/.81 +6kt.
My review of FCOM SYS yesterday does not support that opinion, it seems to imply that red barber is the "Vmo of the moment" and overspeed protection is associated with it (green ticks). More research required, but maybe you already know how it actually is.
Vmax on the speedtape is based on the lowest of Vmo,Mmo,Vle, Vfe.(Barbers pole)
High speed protection is referenced to VMO+6 or Mmo+0.01.(Green equals symbol)
DSC-31-40 Airpseed
High speed protection is referenced to VMO+6 or Mmo+0.01.(Green equals symbol)
DSC-31-40 Airpseed
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FD
Exactly! (VMO+6/MMO+.01) If the ATHR is in Speed mode the FMGS will protect Vfe, Vle. or if flying manually even in THRCLB where the FDs will disappear, ATHR will change to speed with thrust going to idle and managed target speed will become selected.
I had a feeling that barber pole would come down the speed strip with the configuration (Vfe, Vle), however the overspeed protection stays as 350/.81 +6kt.
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Slightly different to the sim I have from Airbus. Obviously what you say is what the FCOM says and that's the bible when it comes to requiring a reference doc.
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There is a operational test procedure of VMO/MMO Over speed Warnings given below. All I could make out from it was it is overspeed warning threshold that is changed and not protection.
B. OVERSPEED Warning VMO/MMO 2 (L/G DOWN VMO/MMO SELECTION Switch 22FP at L/G DOWN)
ACTION RESULT
1.In the avionics compartment, on the panel 188VU:
. remove the lockwire from the safety cover of the L/G DOWN VMO/MMO SELECTION switch.
. set the switch to L/G DOWN.
2.In the cockpit on the overhead panel, on the ADIRS
CDU:
On the ADIRS CDU:
. push the ADR2 and ADR3 pushbutton switches. . the OFF legend of the ADR2 and ADR3 pushbutton
switches comes on.
3.On the MCDU: On the MCDU:
. push the line key adjacent to the ADR1 indication. . the ADR1 page comes into view.
. push the line key adjacent to the OUTPUT TESTS
indication.
. the ADR1 OUTPUT TESTS page comes into view.
. push the line key adjacent to the INTERFACE TEST
indication.
. the ADR1 INTERFACE TEST 1/2 page comes into
view.
. on the keyboard push the NEXT PAGE function key. . the ADR1 INTERFACE TEST 2/2 page comes into view.
. push the line key adjacent to the START TEST
indication.
(Ref. TASK 34-13-00-740-002-A).
From 0 to 10 seconds, ignore the warnings and indications.
From 10 seconds and more, on the CAPT(F/O) PFD, the speed increases to 367.7 Kts. When the value is 239Kts:
. on the upper ECAM display unit, this indication is
shown:
OVERSPEED VMO/MMO 235/.60
. on the panels 130VU and 131VU, the MASTER WARN lights flash.
. you can hear the continuous repetitive chime aural
warning.
. push the line key adjacent to the RETURN indication. The test procedure stops.
B. OVERSPEED Warning VMO/MMO 2 (L/G DOWN VMO/MMO SELECTION Switch 22FP at L/G DOWN)
ACTION RESULT
1.In the avionics compartment, on the panel 188VU:
. remove the lockwire from the safety cover of the L/G DOWN VMO/MMO SELECTION switch.
. set the switch to L/G DOWN.
2.In the cockpit on the overhead panel, on the ADIRS
CDU:
On the ADIRS CDU:
. push the ADR2 and ADR3 pushbutton switches. . the OFF legend of the ADR2 and ADR3 pushbutton
switches comes on.
3.On the MCDU: On the MCDU:
. push the line key adjacent to the ADR1 indication. . the ADR1 page comes into view.
. push the line key adjacent to the OUTPUT TESTS
indication.
. the ADR1 OUTPUT TESTS page comes into view.
. push the line key adjacent to the INTERFACE TEST
indication.
. the ADR1 INTERFACE TEST 1/2 page comes into
view.
. on the keyboard push the NEXT PAGE function key. . the ADR1 INTERFACE TEST 2/2 page comes into view.
. push the line key adjacent to the START TEST
indication.
(Ref. TASK 34-13-00-740-002-A).
From 0 to 10 seconds, ignore the warnings and indications.
From 10 seconds and more, on the CAPT(F/O) PFD, the speed increases to 367.7 Kts. When the value is 239Kts:
. on the upper ECAM display unit, this indication is
shown:
OVERSPEED VMO/MMO 235/.60
. on the panels 130VU and 131VU, the MASTER WARN lights flash.
. you can hear the continuous repetitive chime aural
warning.
. push the line key adjacent to the RETURN indication. The test procedure stops.
Last edited by vilas; 30th Jan 2023 at 04:48.
