Twin Otter Mishap Orchid Island 13 April 17

[armchairpilot94116]

Twin Otter crashes at Orchid Island Airport, 4 injured | Society | FOCUS TAIWAN - CNA ENGLISH NEWS (http://focustaiwan.tw/news/asoc/201704130017.aspx)

https://aviation-safety.net/database/record.php?id=20170413-0

Lucky no one seriously hurt. They had just gotten these not long ago to replace some very old Dornier 228.

[avionimc]

Strong cross winds are manageable with the Twin Otter, but the tiller should not be touched during the landing roll! Or during the take off roll for that matter. It wouldn't be the first time a pilot tries to steer with the tiller and ends up in the ditch:=

[JammedStab]

Very true. We had a new Twin Otter captain do this on takeoff at a military base down in South America. They already were unhappy due to a weather diversion in landing there. They put them under house arrest after their excursion and a new crew had be flown all the way down to pick up the aircraft.

[twochai]

True, but you do need to move your hands and feet - a declining skill, unfortunately!

[Escape Path]

Crosswinds on the Twin Otter are certainly manageable but it keeps you on your toes...

You need to pay attention, the wind hits it a bit harder than other types with that tall tail, though it's the same tail and the massive movement from the rudder what helps you fight the crosswinds.

Could it be a case of improper landing technique?

[The Ancient Geek]

Strong gusting crosswinds are the ones that can catch you out, a sudden gust can have you in the weeds rather quickly. Greasers are bad, you need to get all of the weight on the wheels ASAP.
Probably bad habits by a crew newly converted from the DO228.

[Herod]

Many years ago. Gusting crosswind, which dumped the port wing lower than intended just as aileron effectiveness was lost. The result was the outboard aileron hinge scraping along the runway, until enough speed was lost to allow the aircraft back onto its wheels again. I'm told that from the outside it looked quite spectacular.

[armchairpilot94116]

Orchid Island and Green Island where these planes fly are known to have high winds and similar mishaps have occurred there with the Dornier 228 that they finally retired.

Is the Twin Otter harder to handle in high winds than the Dornier? Could be the pilots transitioning from the Dornier need more time.

[Escape Path]

I didn't fly the Do but I reckon it has higher operational speeds. They're both STOL if I'm not mistaken, but maybe the lower speeds and the higher lift characteristics of the Otter can make for a gust or something to shake it off its path easier?

Though as a pilot you should be able to handle it with proper landing technique. As the ancient geek puts it, no greasers for starters. Using the props in an effective manner is also helpful as it helps to control the "airborne-mind" of the Otter at touchdown when it's carrying a couple extra knots...

[The Ancient Geek]

Indeed, its all about directional stability.
In the air speed = momentum = stability.
On the ground directional stability comes from having the wheels firmly on the ground.
So touching down firmly with a bit of extra speed gets you through the vulnerable bit as quickly as possible. But not enough speed to make it float in ground effect.

All STOL types have this vulnerability due to their low touchdown speed.

[armchairpilot94116]

https://www.youtube.com/watch?v=fjfw60krv68

Any landing that you can use the plane again is a good landing on Orchid Island.

[JammedStab]

The Twin Otter handles a strong crosswind very well. Being a high wing aircraft, you can lower that wing down into the crosswind a significant amount. It has a big rudder which also helps. I don't know the length of this runway but in non-STOL ops at flaps 20, it can still land in a fairly short distance.

The runway looks reasonably long in the video. I think a better landing technique might have been a fair amount of wing down and a better flare instead of forcing it on. The wind wasn't even that strong or at too much of an angle to the runway according to the windsock.

[armchairpilot94116]

Quite a bit of damage:

https://www.youtube.com/watch?v=mbcKiRYBG4M

https://www.youtube.com/watch?v=_XlqHXfdIhU

beyond economic repair perhaps?


Direction Length Surface

13/31 1,123m 3,684ft Paved

Previous Daily Air incident with a Do 228

https://www.asc.gov.tw/upload/acd_att/DA7507_Executive%20Summary.pdf

[The Ancient Geek]

The Twin Otter handles a strong crosswind very wellYup - those oldpharts among us who came to the twotter from the AN2 thought we had arrived in crosswind heaven. But a strong gust could still bite you on the backside.

[9 lives]

That Twin Otter will be rebuilt. If too many "parts" are needed for the repair, it could be that Viking is asked to produce a cockpit subassembly to splice in. Viking has made subassemblies to enable such repairs before. I would expect that it will return by ship to one of several North American facilities for repair.

On the ground directional stability comes from having the wheels firmly on the ground.
So touching down firmly with a bit of extra speed gets you through the vulnerable bit as quickly as possible. But not enough speed to make it float in ground effect.

Or, as long as the weight of the aircraft is not firmly on three wheels, assure that you are still using the flight controls to maintain control. Even with weight on the nosewheel, at "speed", the rudder is effective enough to scrub the tire, which is as it should be - the flight controls maintain control. However, reverse can be a factor too...

Though I have no idea if it a factor in this event, applying reverse too aggressively or unevenly can cause rapid loss of directional control. Reverse interrupts the effective airflow over the tail, so it works much less well to keep the plane straight, and if applied too rapidly, may be unsymmetrical in effect due to spool up times. This has been the cause of a number of Twin Otter and Buffalo accidents.

A Twin Otter is not equipped with anti skid, so on a wet runway, too much application of brakes can get you in trouble, locking wheels, which can then slide sideways.

A 3600 foot runway is ample for a nice unbraked, non reverse, landing in a Twin Otter. "STOL" technique is not required for that runway, and I doubt operationally approved anyway.

[misd-agin]

https://www.youtube.com/watch?v=fjfw60krv68

Any landing that you can use the plane again is a good landing on Orchid Island.


Zero crosswind controls. Makes it look worse than the conditions warrant.

[Escape Path]

1100 meters is enough for a flap 20 landing which helps a bit to fight a crosswind. +1 on the brakes and reverse re Step Turn. You could even afford to fly it down with a bit of power and wing down until touchdown and then using reverse sensibly. A couple of extra knots should help if the wind is particularly strong. Runway surface looks good, braking shouldn't be an issue

Something must have gone particularly wrong in this case.

[avionimc]

https://www.youtube.com/watch?v=mbcKiRYBG4M

https://www.youtube.com/watch?v=_XlqHXfdIhUfrom the first video we notice that flaps are set at 20.

Flaps 20 for normal landings (normal runways).
Flaps 40 only for extremely short runways (e.g., with high trees at each end); or for training.

[9 lives]

Flaps 40 in a Twin Otter requires piloting skills just a little beyond the standard Caravan/Navajo/King Air. It's easy to get too much weight on the nose wheel, or even wheelbarrow it, which I have seen done. The nose wheel area (known as "station 60") is a little vulnerable to hard landings on the nose wheel. I was always afraid to be responsible for damage in general, and station 60 in particular - so I kept the nose light.

I was trained by a DHC test pilot, who would not let me fly 40 flap landings, until I really impressed him with my flaps 20 landings. He also trained me in 30 flap takeoffs, but that's a story for a different time...

The Twin Otter is a very sure plane to fly, so one feels pretty confident handling them - occasionally too confident, perhaps...

[rigpiggy]

That Twin Otter will be rebuilt. If too many "parts" are needed for the repair, it could be that Viking is asked to produce a cockpit subassembly to splice in. Viking has made subassemblies to enable such repairs before. I would expect that it will return by ship to one of several North American facilities for repair.



Or, as long as the weight of the aircraft is not firmly on three wheels, assure that you are still using the flight controls to maintain control. Even with weight on the nosewheel, at "speed", the rudder is effective enough to scrub the tire, which is as it should be - the flight controls maintain control. However, reverse can be a factor too...

Though I have no idea if it a factor in this event, applying reverse too aggressively or unevenly can cause rapid loss of directional control. Reverse interrupts the effective airflow over the tail, so it works much less well to keep the plane straight, and if applied too rapidly, may be unsymmetrical in effect due to spool up times. This has been the cause of a number of Twin Otter and Buffalo accidents.

A Twin Otter is not equipped with anti skid, so on a wet runway, too much application of brakes can get you in trouble, locking wheels, which can then slide sideways.

A 3600 foot runway is ample for a nice unbraked, non reverse, landing in a Twin Otter. "STOL" technique is not required for that runway, and I doubt operationally approved anyway.

Right now there is a japanese twotter in yyj getting rebuilt due to the same finger problem. Basically a new assy from the wings forward.

[Escape Path]

I was trained by a DHC test pilot, who would not let me fly 40 flap landings, until I really impressed him with my flaps 20 landings. He also trained me in 30 flap takeoffs, but that's a story for a different time...

The Twin Otter is a very sure plane to fly, so one feels pretty confident handling them - occasionally too confident, perhaps...

It's pretty easy to feel confident with the Otter, but it can surely bite when one is not expecting it...especially at landing

As for the flap 30 takeoff...I believe there's a crash (on video) in Canada of a failed takeoff in such setting. I've done flap 20 takeoff and it keeps you on your toes, no idea how a flap 30 takeoff would feel.

[sleeper]

This one?

https://aviation-safety.net/database/record.php?id=20070708-0

https://www.google.nl/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3DrLiZBsbWv-0&ved=0ahUKEwiWs4ucyrDTAhXmLsAKHWqIAn4QwqsBCBwwAA&usg=AFQjCNE7Hd1xU6v9oZLnr_l9MawQGwM7lQ

[9 lives]

It's been a long time, but my recollection of the 30 flap takeoff technique was that of being a trained maneuver, which should not be attempted without the training. The video bears that out. I was briefed exactly what to do, and it worked exactly as briefed. I can see that experimentation would end poorly.

That said, the Twin Otter's short field performance is so excellent with the approved takeoff technique, I can't see a need for 30 flap takeoffs in a practical sense - thus it is, and should be an unapproved maneuver. I think for me, it was just a training exercise (mostly in following a briefing during a challenging operation!).

During my experience with STOL modified Cessnas and other light types, I find that there is often an over eagerness to peel the aircraft off the surface at the first possibility, and then steeply climb away at the slowest airspeed - for zero operational need. High risk, no reward. With GA flying, that foolishness is impossible to regulate. With the Twin Otter, which is nearly always flown in an "operator" environment, it's easier to limit the types of activities. There are distinctly non STOL flying techniques published for the Twin Otter, which are perfectly suitable for most operations.

[JammedStab]

Most likely for off-strip operations perhaps on very soft ground or skis on soft or wet snow. Have to admit that I never actually saw it done, just heard about it.

[Escape Path]

This one?

https://aviation-safety.net/database/record.php?id=20070708-0

https://www.google.nl/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3DrLiZBsbWv-0&ved=0ahUKEwiWs4ucyrDTAhXmLsAKHWqIAn4QwqsBCBwwAA&usg=AFQjCNE7Hd1xU6v9oZLnr_l9MawQGwM7lQ
Yup, that's the one

We used to do flap 10 takeoffs, our normal operation didn't need more than that. We did flap 20 takeoffs in training as a demonstration maneuver. It needs to be a very conscious maneuver as you can get in serious problems very easily if you don't know what you're doing. Rotation speed is below Vmca, for starters...

Still, it's a fun thing to do

[Dufo]

Which performance regulations allow Vr to be below Vmca?

[Herod]

IIRC, Perf C in the UK. That also allows, among other things, the assumption that an engine failure will not occur below 50' agl. I'm way retired, and my Otter days are nearly forty years in the past, so excuse any errors.

[khorton]

Which performance regulations allow Vr to be below Vmca?
The Twin Otter Series 100, 200 & 300 were approved to the US Civil Air Regulations Part 3, at amendment 8, which allowed Vr to be below VMCA. Certain later operating rules applicable to some operations require Vr to be above VMCA - the published performance covers both options. Some operators use Vr < VMCA, and others use Vr > VMCA.