United Express (opr by Trans States) runway overrun in YOW

[Go Guns]

spend millions on putting shops and bars into an airport terminal and not spend a cent on improving operational facilities

While I agree to your line of thought, it's not relevant to this incident.

[Liquid Charlie]

While I agree to your line of thought, it's not relevant to this incident.

-- I did mention grooved runway

[swordfish]

Ottawa is not busy enough nor is the weather often poor enough to require a CAT II.

that has to be one of the silliest replies i have ever read and I must say typical canadian aviation thinking -- spend millions on putting shops and bars into an airport terminal and not spend a cent on improving operational facilities -- like a grooved runway and a cat 2 landing -- seems that places like Europe figure it's good policy and airports far less busy that Ottawa have it -- I'm sure wpg has no more "bad"wx than ottawa -- go figure -- only in canader -- silly

+1
In Europe almost every village, town, and city has an ILS and most of the larger cities are set up with Cat IIIb facilities. After the ILS is installed, the associated ground infrastructure is the least expensive part of it. Tho it will take NavCanada 2 years to publish the plate...

[linecrew]

While I agree to your line of thought, it's not relevant to this incident.

-- I did mention grooved runway

The airport has never had grooved runways since they were built back in the 50's and you'd be hard pressed to find incidents of aircraft sliding off (outside of winter ops) except in the last handful of years.

Are some modern aircraft like the early model ERJs not able to handle this type of runway surface? Is it the calibre of crews flying in there? I just don't get how this has 'suddenly' become a problem.

[CpnCrunch]

It seems odd to select maximum thrust for 7 seconds at 5 feet AGL. Shouldn't they have either just let the aircraft settle onto the runway, or else fully committed to a go-around?

[flyinhigh]

Lack of experience is the reason here. 2 reasons that stand out are;

1. In a storm with high winds they selected full flap coming through 1000'. Now your changing configuration in deteriorating weather conditions. Can anyone say unstable approach already.

2. Max reverse selected while aircraft is in the air. (Selected max reverse at 5' agl for 7 seconds), sry you hit reverse while in the air....If you wanna do this do a go around, obviously your already worried.

[av8ts]

Lack of experience is the reason here. 2 reasons that stand out are;

1. In a storm with high winds they selected full flap coming through 1000'. Now your changing configuration in deteriorating weather conditions. Can anyone say unstable approach already.

2. Max reverse selected while aircraft is in the air. (Selected max reverse at 5' agl for 7 seconds), sry you hit reverse while in the air....If you wanna do this do a go around, obviously your already worried.

I think that was max thrust not max reverse thrust

[CpnCrunch]

Lack of experience is the reason here. 2 reasons that stand out are;

1. In a storm with high winds they selected full flap coming through 1000'. Now your changing configuration in deteriorating weather conditions. Can anyone say unstable approach already.

2. Max reverse selected while aircraft is in the air. (Selected max reverse at 5' agl for 7 seconds), sry you hit reverse while in the air....If you wanna do this do a go around, obviously your already worried.

I think that was max thrust not max reverse thrust

Yes, and the report says the aircraft wasn't equipped with reverse thrust (and that was a factor in the overrun).

[Donald]

While I agree to your line of thought, it's not relevant to this incident.

-- I did mention grooved runway

The airport has never had grooved runways since they were built back in the 50's and you'd be hard pressed to find incidents of aircraft sliding off (outside of winter ops) except in the last handful of years.

07/25 is in fact grooved, it was done after it was re-paved recently.

And it has made a tremendous difference on rainy days.

[linecrew]

07/25 is in fact grooved, it was done after it was re-paved recently.

And it has made a tremendous difference on rainy days.

Yeah...they grooved it because the *same company* ran an exact same type of aircraft off the end of Runway 07 in 2010: http://www.tsb.gc.ca/eng/medias-media/c ... 130613.asp

I still question how this is now suddenly considered a huge safety enhancement when, up until just recently, aircraft operated safely on these runways without the aid of grooving for several decades.

[pelmet]

Completed reading the report recently. Definitely some odd stuff happened on this flight. To begin with, this was one of the last flights that this company(Trans-States Airlines) was operating into Ottawa. The airline had already had two rain-related runway excursions at YOW. One in 2004 on runway 25 and one the previous year on runway 07. So, what did the airline do about it? They banned landings on runway 07/25 if it was wet or damp, meaning that only 14/32 could be used(it is a longer runway). However, since the accident in the previous year, runway 07/25 had been grooved(the only runway in Canada at that time according to the report).

As is so often the case in these types of accidents, it started raining heavily as the aircraft was on approach. The winds did pick up and were straight down 32 at 13 gusting up to 20 knots. Because of this, the Vapp target was increased by 7 knots to 140. A couple of minutes prior to touchdown, a special weather report showed the visibility of ½ mile in heavy rain.

With heavy rain at the airport and a non-grooved runway, the risk of hydroplaning was significant. Unknown the crew was an increased risk of hydroplaning for this particular aircraft because three of the four main tires were a bit under-inflated.

The TSB states that the aircraft was flown in an unstable manner both on approach(due to flap configuration not being set and being 41 knots fast at the FAF) but more importantly, with regard to crossing the threshold with the speed the speed still being 11 knots above target). The crew were able to slow down to the Vapp of 140 with landing flap(although the TSB calculations show that it should have been set to 142), but a quote from the airline’s SOP says that at 200 feet above the airport, the power is reduced slightly in order to reduce the speed from Vapp to Vref(nothing is mentioned about keeping some extra speed for the gusty winds). This procedure seems a bit odd to me. Boeing says to bleed off the headwind correction only but not the gust additive while Airbus holds Vapp to the flare. However, the TSB felt that all additives should have been bled off for the touchdown as per company SOP(I am not sure if this procedure comes from Embraer).

Power was reduced at 20 feet and the flare initiated in increasing rain intensity to a point where a sudden downpour obscured the pilot’s view of the runway. At 5 feet above the runway, the captain added maximum thrust for 7 seconds. This obviously extended the flare and instead of a proper firm touchdown in such conditions in order to reduce the risk of hydroplaning, there was a smooth touchdown 2700’ from the threshold. The aircraft became airborne again briefly with a second touchdown just beyond the 3000 foot mark. The report noted that a 5% increase in landing speed increases landing distance by 10%. Aircraft floating to bleed off speed also increases landing distance versus that speed decreasing during a landing roll.

Although company SOP’s state that a firm landing should be used on wet runways to allow the tires to break through any water film, the report states that this captain used dry runway landing techniques as standard practice for all his landings.

This particular aircraft was one of several in the company’s fleet that did not have thrust reversers, making it more vulnerable once in a hydroplaning situation.

The captain applied maximum braking as per company SOP and the airplane started skidding right away, so he asked for the F/O to also apply maximum braking. Max braking is recommended by the company SOP in such runway conditions, however, activating the Emergency/Parking Brake is not SOP, yet this handle was partially activated during the skidding event and was further activated when no braking was felt but was stowed when it had no effect. It should be noted that using the emergency/parking brake de-activates anti-skid( which slowed tire rotation) and deactivates the spoilers.

About 7500 feet from the threshold, the aircraft started to skid more and more sideways and track toward the runway edge until it departed the runway and the main gear collapsed with the aircraft facing to the west. A special weather report 5 minutes after the accident showed that the wind was straight out of the west gusting to 25 knots, so it is unknown when this change happened but the aircraft’s tail did swing to the right during the landing roll which makes me suspect that there was a wind direction shift from the last reported wind that was straight down the runway.

The TSB extensively discussed hydroplaning issues in the report. With regard to water, a runway is considered to be contaminated when the water depth is 3mm. However, NASA states that hydroplaning can start with just over 2.5mm water depth(water depth at YOW was estimated to be 4-6mm). The formula for the minimum hydroplaning speed is 7.7 times the square root of the tire speed(a formula that many of us memorized) but NASA states that this is only for a non-rotating tire at touchdown. Based on the table in the report, for a rotating tire, the minimum hydroplaning speed(a speed that we would like be below) is around 15 knots higher.

There are three types of hydroplaning which all of us should be aware of. Because of the water depth, the report stated that dynamic hydroplaning was encountered followed by reverted rubber(which the report states usually follows the dynamic type), which I assume is because the surface changes from pooled water to wet runway with no significant depth.

The report states that anti-skid systems work very well on surfaces that do have friction but are not very effective once the surface becomes flooded. Brake modulation at high hydraulic pressures at the anti-skid system is very effective but in low friction situations like a flooded runway, the hydraulic pressure to the system is very low and therefore sluggish in response. In addition, the anti-skid system uses a comparison of actual wheel speed to a calculated reference value for optimum braking(if the difference becomes too big, braking pressure is released). But if there is no reference speed to begin with because the wheel did not spin up, there is no anti-ski action and with the pilot applying brakes, the stops and it is locked on that water surface(and acts like the call sign of the airline) and then starts its reverted rubber skidding when the contaminated surface changes to a normal wet surface asphalt. Therefore, the way to reset the anti-skid is to momentarily release the brakes and perhaps wait until the contaminated surface ends and normal wet runway conditions are encountered(similar might apply to a frozen very slippery surface such ice patches). Keeping the brakes applied creates a situation where wheel speed is significantly different from groundspeed which can result in anomalous anti-skid behaviour.

The report then discussed the loss of directional control while skidding. According to the AFM issued by Embraer, the pilot should keep braking when no braking action has been felt, even if directional control has been lost. This differs from other manufacturers that state that there should be an immediate, momentary release of brake pressure in the event of directional control loss in order to allow the wheels to spin up.

The report then discusses the use of differential braking in such a situation. Under normal conditions, where more brake pressure equals more braking action, increased pressure on a brake pedal equates to an increased amount of braking action on that side and therefore an increased rate of turn of the aircraft in the same direction as the pedal that the pressure is applied to. Most pilots have become instinctively used to this reality.

However, in a situation where brakes are being applied and anti-skid then activates, brake pressure is now being released by the anti-skid. Therefore, in order to utilize differential braking to change direction, one has to initially release brake pedal pressure on the pedal in which one wants turn(and once braking capability is re-established, then re-apply brake pedal pressure). This initial action is the opposite of what a typical pilot is used to, as the situation is extremely rare and not spelled out much in publications. The pilot is also in a critical situation where instinct is more likely to happen.

The company SOP of always applying maximum braking in such conditions conflicted with the NASA recommendation of exercising caution with regard to brake application above the hydroplaning speed on a wet runway. Of course, one might say that this is difficult to do in the conditions encountered in such a situation but like the shifting, strong winds and poor visibility….anything can happen in a heavy rainstorm and you may want to avoid landing in those conditions, especially on an ungrooved runway.

Bottom line, all kinds of unpredictable and undesirable things can happen in heavy downpours, from strong and shifting winds, zero visibility, windshear, zero braking, etc. Why not break off the approach and hold until conditions are better or divert. With no reversers, stopping is more difficult, especially on ungrooved runways.

The TSB final report is fairly well done. Too bad they make it so difficult to get laboratory reports(have to be done through a cumbersome ATIP request), unlike the American NTSB that makes it so easy.

[Canoehead]

At 5 feet above the runway, the captain added maximum thrust for 7 seconds

Been a long time since I read this report, but 7 seconds?

I would have been about 6 seconds into a go-around in that case.

I might need to read that again.

[pelmet]

One can only guess for the reasons but I suspect that power was added after sight of the runway was lost, then he saw it again and decided to land.

All three incidents appear to be pilot incompetence with multiple examples. And guess what....Trans-States and the insurance company sued the Ottawa airport to recover money.

https://ottawacitizen.com/news/local-ne ... ff-runways