Mahan B146-300 damaged in overrun at Khark
Points to ponder:-
Beware marginal tailwinds. 146/RJ 10 kt limit vs higher reported?
Consider a dry dusty runway as a form of contaminant.
Double check the deployment of lift dump / spoilers. Speculation from photos.
Go Around from the runway if the touchdown point is further than that planned.
"A landing is an approach without a go around."
Consider a dry dusty runway as a form of contaminant.
Double check the deployment of lift dump / spoilers. Speculation from photos.
Go Around from the runway if the touchdown point is further than that planned.
"A landing is an approach without a go around."
146/RJ has a 15 knot tailwind limit.
Even with 20 knots of tailwind and a wet runway you should be able to land in 2334m with full safety factors and room to spare. Landing charts have the wind factored by 50% so you should actually be able to do it with 30 knots of tailwind! I don't think you can blame it on a reported 15 knots tailwind vs an actual of 20 knots or something.
Wing does look suspiciously clean
Even with 20 knots of tailwind and a wet runway you should be able to land in 2334m with full safety factors and room to spare. Landing charts have the wind factored by 50% so you should actually be able to do it with 30 knots of tailwind! I don't think you can blame it on a reported 15 knots tailwind vs an actual of 20 knots or something.
Wing does look suspiciously clean
Aero, the 146's higher tailwind clearance was originally limited to specific operators / operations according to each aircraft's flight manual.
The Australian clearance may have been the first, to allow night freight operations into Sydney(?).
The AFM amendment should have specific limitations and training requirements. However, some sold-on aircraft took the 15 kt tailwind clearance as verbatim, similarly so did some national authorities without further thought and enabled the higher limit without AFM amendment.
Tailwinds are notoriously hazardous because they quickly decrease the landing distance margins. Although book figures and extrapolation might suggest that a landing is feasible, this assumes that the ideal touchdown point is achieved, that the pre landing calculations are realistic, speeds accurately flown and the runway braking action is as expected.
Tailwinds tend to displace the touchdown point into the runway and increase the flare time/ distance, which together with an increased tendency to float, can negate all safety margins and more ... Check yours understanding of the 50% tailwind factor; it is a necessary requirement and not to be assumed as additional margin to be traded.
One of the 146's approach characteristics is that the pitch attitude approximates to the flight path. Tailwinds tend to increase the relative (air mass) flight path (more nose down pitch), which may encourage pilots to revert to a lower nose-down attitude after touchdown with more forward stick than usual. Excessive nose down input can lift the main wheel oleos above the on-ground microswitch setting which delay/ prevent lift dump deployment. As the airspeed reduces then the switches should close and the spoilers deploy ... ... providing that they have been selected and/or the system has not malfunctioned (normally associated with an amber alert).
cf steep approach into LCY, where there have been a few spoiler incidents, and note that the 146-300 (RJ100) has no tailwind capability on a 5.5 deg GS ... AFM limitation.
The RJ has auto spoiler, but this system still requires the on-ground micros witches to be closed (IIRC this involves an interesting 2 out of 3 logic involving the nose wheel to counter a wing lifting in a crosswind and preventing main wheel contact.)
The Australian clearance may have been the first, to allow night freight operations into Sydney(?).
The AFM amendment should have specific limitations and training requirements. However, some sold-on aircraft took the 15 kt tailwind clearance as verbatim, similarly so did some national authorities without further thought and enabled the higher limit without AFM amendment.
Tailwinds are notoriously hazardous because they quickly decrease the landing distance margins. Although book figures and extrapolation might suggest that a landing is feasible, this assumes that the ideal touchdown point is achieved, that the pre landing calculations are realistic, speeds accurately flown and the runway braking action is as expected.
Tailwinds tend to displace the touchdown point into the runway and increase the flare time/ distance, which together with an increased tendency to float, can negate all safety margins and more ... Check yours understanding of the 50% tailwind factor; it is a necessary requirement and not to be assumed as additional margin to be traded.
One of the 146's approach characteristics is that the pitch attitude approximates to the flight path. Tailwinds tend to increase the relative (air mass) flight path (more nose down pitch), which may encourage pilots to revert to a lower nose-down attitude after touchdown with more forward stick than usual. Excessive nose down input can lift the main wheel oleos above the on-ground microswitch setting which delay/ prevent lift dump deployment. As the airspeed reduces then the switches should close and the spoilers deploy ... ... providing that they have been selected and/or the system has not malfunctioned (normally associated with an amber alert).
cf steep approach into LCY, where there have been a few spoiler incidents, and note that the 146-300 (RJ100) has no tailwind capability on a 5.5 deg GS ... AFM limitation.
The RJ has auto spoiler, but this system still requires the on-ground micros witches to be closed (IIRC this involves an interesting 2 out of 3 logic involving the nose wheel to counter a wing lifting in a crosswind and preventing main wheel contact.)
Safetypee, you know a lot more about the history than I do. All I know is how they are now. The fleet currently operated in Australia, including all variants, have a 15 knot tailwind limit as standard. The freighters, -100 and -300 models, have a supplement to allow landing with 20 knots of tailwind into Sydney on RW34L. Tabulated data for this is provided in the company ops manuals and includes an additional 10% safety factor on top of the already included 67% for dry and 93% for a wet runway.
That data shows the runway required at max landing weight, on a wet runway, at ISA+20, is about 2300m.
I wasn't suggesting that the 50% wind factor is there to be intentionally used, only that if the reported wind is 15 knots and you cross the fence with 17 knots tail, it shouldn't adversely affect your ability to land within the calculated landing distance.
My point is that a tailwind of around 15 knots on a dry >2300m runway should pose no issues at all for a competent crew.
As you say there are some traps to be avoided when landing with a strong tailwind. If you start down the slope without being fully configured it can be difficult to get slowed down. This is particularly true when there is a bit of a wind gradient. 15 knots tail on the ground might be 40 knots at 3000'. I haven't personally noticed a tendency to land nose low but both you and the FCOM mention it so I'm sure it has caught pilots out in the past.
Some 146s have quite stiff thrust levers and I have seen, on more than one occasion, pilots fail to select ground idle on touchdown. This is specially a problem if you fly the RJ and the 146 as the RJ FADEC does this for you.
So with the reported conditions the landing was well within the capabilities of the aeroplane. However a strong tailwind can easily lead to a fast approach which may lead to a long landing. Combine that with a failure to select ground idle and spoilers and you quickly eat up the available runway. A possible scenario.
That data shows the runway required at max landing weight, on a wet runway, at ISA+20, is about 2300m.
I wasn't suggesting that the 50% wind factor is there to be intentionally used, only that if the reported wind is 15 knots and you cross the fence with 17 knots tail, it shouldn't adversely affect your ability to land within the calculated landing distance.
My point is that a tailwind of around 15 knots on a dry >2300m runway should pose no issues at all for a competent crew.
As you say there are some traps to be avoided when landing with a strong tailwind. If you start down the slope without being fully configured it can be difficult to get slowed down. This is particularly true when there is a bit of a wind gradient. 15 knots tail on the ground might be 40 knots at 3000'. I haven't personally noticed a tendency to land nose low but both you and the FCOM mention it so I'm sure it has caught pilots out in the past.
Some 146s have quite stiff thrust levers and I have seen, on more than one occasion, pilots fail to select ground idle on touchdown. This is specially a problem if you fly the RJ and the 146 as the RJ FADEC does this for you.
So with the reported conditions the landing was well within the capabilities of the aeroplane. However a strong tailwind can easily lead to a fast approach which may lead to a long landing. Combine that with a failure to select ground idle and spoilers and you quickly eat up the available runway. A possible scenario.
Join Date: May 2004
Location: Balmullo,Scotland
Posts: 932
Likes: 0
Received 0 Likes
on
0 Posts
As an engineer have never worked on the 146 just wondered if the wing spoilers can be MELd? or is there an auto retraction function with loss of hydraulic/electrical power?
Spoilers themselves can't be MEL'd but the various spoiler indications can be.
The deploy valve requires electrical power. If power is lost the valve moves to the retract position, however the spoilers require hydraulic pressure to retract so if hydraulic pressure was removed first I guess they'd still be deployed but if electrical power was removed first they could be retracted when they had previously been deployed.
In short, I don't think anything can be inferred from the position of the spoilers in the photos.
The deploy valve requires electrical power. If power is lost the valve moves to the retract position, however the spoilers require hydraulic pressure to retract so if hydraulic pressure was removed first I guess they'd still be deployed but if electrical power was removed first they could be retracted when they had previously been deployed.
In short, I don't think anything can be inferred from the position of the spoilers in the photos.
Join Date: May 2004
Location: Balmullo,Scotland
Posts: 932
Likes: 0
Received 0 Likes
on
0 Posts
Aerocat thanks for that my only thought is retraction after electrical power loss may have occurred by residual hydraulic power if this was a fairly rapid event?
Join Date: May 2004
Location: Bear Island
Posts: 598
Likes: 0
Received 0 Likes
on
0 Posts
overrun on a 2300m runway with the Bae146 is the province of African airlines with no coherent safety culture (I used to work for one who achieved exactly the same and flouted safety culture at every opportunity, so I know the subject well)
A fully loaded 146 even on a summers day into LCY requires between 50 /60% LDA.
There is no excuse for departing the upwind end of a 2300m runway in a BAe146.
A fully loaded 146 even on a summers day into LCY requires between 50 /60% LDA.
There is no excuse for departing the upwind end of a 2300m runway in a BAe146.
