Speed Got Too Low

[pelmet]

2000 fpm required. Is that easy at 330? Might depend on the OAT. The thing is that you have a very strong incentive to climb and are tempted to keep slowing down. Best to wait....

C-GDMP, a WestJet Boeing B737-800 was operating flight WJA2194 from Victoria International
Airport (CYYJ), BC, to Cancún International Airport (MMUN), MX. WJA2194 was cleared to climb
from FL330 to FL370 with an ATC-issued requirement to complete the climb within 2 minutes.
Clearance was accepted but when passing through FL360, a reduced rate of climb was initiated in
response to a low-airspeed condition as the airspeed was continuing to decay below the minimum
maneuvering speed. The nose was lowered to recover airspeed resulting in a briefing descent to
FL355. During this period, ATC issued a traffic alert for an aircraft at FL360 crossing, left-to-right.
The flight crew received a TCAS TA and advised ATC they had traffic in sight. The traffic crossed
ahead of WJA2194 with 7.44 NM lateral separation, followed by a minimum post-crossing
separation of 0 fee vertically and 4.08 NM laterally as the aircraft diverged, compared to the
required minimum separation of 1000 feet vertically and 5 NM laterally.

[Eric Janson]

2000 fpm required. Is that easy at 330? Might depend on the OAT. The thing is that you have a very strong incentive to climb and are tempted to keep slowing down. Best to wait....

C-GDMP, a WestJet Boeing B737-800 was operating flight WJA2194 from Victoria International
Airport (CYYJ), BC, to Cancún International Airport (MMUN), MX. WJA2194 was cleared to climb
from FL330 to FL370 with an ATC-issued requirement to complete the climb within 2 minutes.
Clearance was accepted but when passing through FL360, a reduced rate of climb was initiated in
response to a low-airspeed condition as the airspeed was continuing to decay below the minimum
maneuvering speed. The nose was lowered to recover airspeed resulting in a briefing descent to
FL355. During this period, ATC issued a traffic alert for an aircraft at FL360 crossing, left-to-right.
The flight crew received a TCAS TA and advised ATC they had traffic in sight. The traffic crossed
ahead of WJA2194 with 7.44 NM lateral separation, followed by a minimum post-crossing
separation of 0 fee vertically and 4.08 NM laterally as the aircraft diverged, compared to the
required minimum separation of 1000 feet vertically and 5 NM laterally.

This is a textbook example of what not to do.

The correct response to a request like this from ATC is "Unable".

Once you accept the clearance you have to follow it.

The worst possible case is accepting and then being unable to meet the restriction and advising ATC.

You are now at an altitude where there is a potential conflict and this is exactly what happened here.

Use of Vertical Speed mode (which looks to be the case in this event) does not give speed protection and needs to be used with caution at high altitudes.

On the A340 I would brief this scenario as part of a Line Check - you'd frequently be looking at 500fpm (or lower) rates of climb. In addition the FMGC predictions were never accurate - people used them anyway! My experience taught me to never accept any climb restrictions as the aircraft simply didn't have the performance.

I spent years operating out of the Middle East with the aircraft very close to maximum allowable weights - we'd get 1200fpm as the highest rate of climb after using most of a 12900' runway to get airborne.

Climbing out of an airport surrounded by mountains I watched one Captain look at the climb predictions (showed 6000' higher than the constraint) and then fly the normal climb profile. I was watching as we crossed the waypoint only 2500' above the constraint.....

This is the sort of stuff that should be covered during Line Training and refreshed during Line Checks.

[Daniel Cooper]

Amazing Airbus gets away with their ridiculous performance.

[flyinhigh]

Another issue here that I see all the time is that one is climbing long at 290 kts, pull the speed back immediately to 250 which the plane does and expedites until 250. Except 2000' later it planes out and does a normal climb rate, thus ending in the same result.

If it does not work, UNABLE..

[nohojob]

Victoria from Cun is about 6 hours.
So this plane was loaded with fuel.
So unless there were few pax, it certainly couldn't achieve this rate of climb.

[Eric Janson]

As a Pilot you should know your aircraft and what its capabilities are.

That should be part of initial line training.