Max Go-Around Pitch Limit 15 degrees with G+B failure on A320

[Minderbinder]

Can anyone explain the go around pitch limit of max 15 degrees when experiencing double HYD G+B and B+Y
on the A320 with FWC standard H9F9D? And why is there no pitch limit in case of going around with a G+Y HYD failure?
Many thanks for the help.

[Goldenrivett]

Probably due to only one elevator working with loss of G+B or B+Y, so pitch control is more sluggish.
With Blue Hyds Available, you have full elevator control.

[underfire]

I think on the Bus you will find the pitch limit in other places, so the "no pitch limit" you reference needs careful review. As you mention an active pitch limit, can you provide more detail?

Under Normal Law, Attitude protection, the ac is pitch limited to 30 degrees up and 15 degrees down.

As noted before in other posts, the if/then, if/then, if/ then...system parameters must be read in their entirety.

[Zaphod Beblebrox]

15 degree pitch limits were a standard on older aircraft. Original DC-9 and B727 series and other aircraft of that generation limited pitch to 15 degrees because the air data systems were not as capable, nor designed to program a flight director with real time data in the event of an engine failure.

Limiting pitch to 15 degrees on the old B737-100 with dash 15 engines meant that the aircraft would accelerate during climb but if was felt that 15 degrees would satisfy the requirement for control ability in the event of an engine failure.

The MD-80, first delivered in the early 1980s, had a flight director / air data system that was programmed for good pitch data in the event of an engine failure. It would give pitch commands to maintain V2+10 and no less than V2. A V2 cut in a Mad Dog is a real chore and requires a both hands on the yoke push to the pitch bar while keeping the wings level. Engineers at McDonald also admitted that one of the reasons for the pitch commands going to V2+10 was for noise abatement.

One way to reduce the noise footprint was to program the flight director to get the maximum altitude possible as quickly as possible. When measuring noise in a standardized manner, for certification purposes, if all things are equal, the aircraft with the higher altitude will register less noise than the same aircraft under the same conditions at a lower altitude.

To get back on point, the A320 is limited in pitch, with hydraulic failures, to allow the pilot sufficient control to quickly maintain the required lower pitch in the event of an engine failure. Pitch authority is limited given the conditions shown by the original poster.

[underfire]

To get back on point, the A320 is limited in pitch, with hydraulic failures, to allow the pilot sufficient control to quickly maintain the required lower pitch in the event of an engine failure. Pitch authority is limited given the conditions shown by the original poster.

Under Normal Law, Attitude protection, the ac is pitch limited to 30 degrees up and 15 degrees down.

And why is there no pitch limit in case of going around with a G+Y HYD failure?

The pitch limits, or lack of limits, in the OP, dont make sense, especially the lack of limits. ie Is the 15 degree limit mentioned in the OP up or down?

[RUMBEAR]

I just checked our FCOM. This pitch limit applies only to our most recent aircraft delivery. All others aircraft in the fleet don't have the same limit following a B+Y or G+B HYD system Fault.

The actual status message is:

FOR GA: MAX PITCH 15 DEG

when I first read it, I assume 15 degrees up only but it doesn't actually say that?

As to why? Hopefully someone better informed can enlighten us as the change with the latest computer versions.

[Zaphod Beblebrox]

The pitch limits, or lack of limits, in the OP, dont make sense, especially the lack of limits. ie Is the 15 degree limit mentioned in the OP up or down?

I believe it's an up limit and it is a pilot limit caution. I don't know about flight director or autopilot function.

[vilas]

Goldenrivett
Probably due to only one elevator working with loss of G+B or B+Y, so pitch control is more sluggish
But why only with a particular FWC? It is not applicable to other aircraft.

[Goldenrivett]

Hi vilas,

I'm just guessing - but have you noticed the change to Vref on the newer aircraft?
If you look at QRH PER A Speeds and compare 320NEO with 320CEO, weight for weight GD speeds are almost identical but VREF speeds are higher on the NEO and remain at 116 kts for weights below 50 tons. (I guess for VMCL reasons)

I thought there may be a similar problem with pitch / power couple control at light weights and low VREFs during the GA with loss of one Elevator. I guessed the guidance was to limit the pitch to 15 degs NU and accept the increase in speed.

[vilas]

Goldenrivett
If you have access to Modification Operational Impact for the FWC F2H9D it will give the effects or impact of this MOD on various systems.

[underfire]

Under Normal Law, Attitude protection, the ac is pitch limited to 30 degrees up and 15 degrees down.

FOR GA: MAX PITCH 15 DEG

Read in the entirety, instead of 30 up and 15 down...you are 15 up/down.

Midbender, in your information, what does it state to add to VREF under those varied conditions? I guess what are the differences on the VREF between all of the conditions.

[Speedwinner]

Any news on that one?

[vilas]

It's five year old thread. With G+B fail 15° pitch limit during a GA it just that, during a GA. And it's for the pilot to ensure that. Aircraft is in Direct Law there are simply no protections. With only half elevator available precise pitch control is difficult more so at approach speeds. That's why even in approach the gear is lowered at 200kts. For Neo the reference speeds are lower than CEO because in A320
VLS= k×Vs1g with 1.23 ≤ k ≤1.28 and VLS ≥ VMCLSharklets reduce VS1g but the the bigger engine increases the VMCL. So if you see Vref it's 5kts less that CEO till 116kts then remain constant. CEO Flap3 speed are higher than Vref by about 5kts but in Neo they are higher by 10kts making Flap3 speeds same. This is possibly for better tail clearance. G+Y full elevator control is available so no pitch restrictions are imposed in a GA.