[Waldo Salt]

This place is to learn from other’s mistakes yeah?
So here’s mine

Not too long ago, I was flying a tailwheel permit aircraft with a continental C 90 engine, into a strip that I had not visited before.

The wind had picked up since I had left my home strip and become gusty, but nothing significant. The strip was easy to find and after arriving overhead I pulled carb head to hot and descended dead side to fly a noise abatement circuit, turning onto final at 500’ QFE for a glide approach. I pushed carb heat cold at about 200’ and touched down smoothly and slowly but as I rolled out the engine stopped. A gust of wind tried to blow the aircraft away from the centre line and I applied opposite rudder. With no slipstream over the tailplane, this worked but with limited effect. Basically, without an engine, I no longer had sufficient directional control. Another, longer gust and I was off to the edge of the runway where I braked to a halt, restarted and, taxied to parking.

So what happened? Temperature was 20° with relative humidity 46%. On a carburettor icing probability chart this indicates moderate icing at cruise power and serious icing at descent power. So carb icing had got me!

On the power checks and flight back, the engine didn’t miss a beat. But when landing, that carb head stayed on until I was off the runway!

What I'm going to do differently in the future:
Review the probability of carburettor icing as part of my preflight checks. Especially if I'm behind a Continental engine.
Keep carb. heat on until I’m off the runway.

[Flyin'Dutch']

Veritable ice makers some engine/airframe set ups.

O200 in Cessnas O540 in Maule.

[Miscellaneous]

Has me pondering what sort of crosswind would be required for this to be an issue for the average permit aircraft? I guess at tick over there is a fair slipstream.

Thanks for posting and giving me something to think about,

[Waldo Salt]

Without slipstream, it makes a big difference! Not been able to find anyone else posting a similar story though.

[Waldo Salt]

This seems similar to me, and lost a Hurricane due to reduced airflow over the rudder.
From the AAIB bulletin at https://assets.publishing.service.gov.u ... 1-2020.pdf (page 76 onwards) 'A tail-down attitude on the ground results in some blanking of airflow over the rudder and fixed fin. Reduced airflow over the fin reduces the weathercock tendency but also reduces rudder effectiveness. If the loss of rudder effectiveness is greater than the reduction of weathercock tendency, the overall effect is to make the aircraft less controllable in yaw when the tail is down.' and the conclusion 'The reported application of brake and an absence of tail-down elevator coincided with the aircraft bouncing and pitching forward on the hard, undulating runway surface, aggravating the effects of the swing. In the absence of effective control inputs to oppose the swing, the aircraft began to slide sideways, eventually causing the landing gear to collapse.'

Article from The Telegraph 14/11/20 below

It took 78 years and £2 million in restoration costs to return the World War Two Hurricane fighter to the skies, but only a 20 minute flight to wreck it.

The plane, which flew during the Battle of Britain, was only in service for four days before it was shot down over Kent by a German Messerschmitt Bf109 on September 28 1940.

Landing in a bog near Canterbury, it lay undiscovered for decades until the 1990s when it was excavated by a group of metal detectorists.

It wasn’t until August 2018, following a two year restoration costing £2 million, that it flew again and has since clocked up around 34 hours of flying time.

But more bad luck struck the iconic plane on June 1 of this year after a 20 minute maintenance flight, when its undercarriage collapsed as it landed at Duxford Airfield, Cambridgeshire.

A report by the Air Accidents Investigation Branch (AAIB) partly blamed the accident on the unidentified pilot for failing to properly control the aircraft.
The Hurricane plane after it was restored took to the skies for the first time in 2018
The Hurricane after it was restored took to the skies for the first time in 2018 Credit: Nigel Iskander / SWNS

It also found that an 11mph crosswind had helped cause the 350mph aircraft to "bounce" and veer to the right on the hard grass runway, putting pressure on the undercarriage.

The 60-year-old pilot walked away unhurt from the stricken plane before it was sprayed with foam by the airfield's firefighters to prevent a blaze.

The plane is now undergoing restoration once again, with hopes it will be up and flying again by next year, according to Andrew Wenman, of Hawker Restorations which carried out the original restoration works, and retained ownership of 25 per cent of the plane.

Commenting on the incident, Mr Wenman told The Telegraph: “I was very grateful no one was hurt... It's obviously heartbreaking for it to happen, we've just restored it and released it, we want it to be up in the sky doing its thing.”

The restoration was led by neurosurgeon Peter Kirkpatrick, a qualified pilot and a neurosurgeon at Addenbrooke's Hospital, Cambridge. In January he revealed that he hoped to fly the Hurricane at air shows.

[TopCat]

What I'm going to do differently in the future:
Review the probability of carburettor icing as part of my preflight checks. Especially if I'm behind a Continental engine.
Keep carb. heat on until I’m off the runway.

I'd agree with this.

I've had carb icing loads of times on the ground, but never in the air. So I've never felt the need to change what I was taught - which was to leave carb heat hot at all times when operating under low power, including all the way down final.

I know that students are often taught to return carb heat to cold on final, presumably to reduce the workload in a go-around situation, but FWIW, I've never really agreed with this.

Going around really shouldn't be a drama, and certainly doesn't need sudden violent actions where there isn't even the time to push carb heat back to cold either with the throttle or just before. I certainly wouldn't want to be slamming the throttle open in any case - a steady three second push is plenty fast enough, and getting the carb heat in before that takes no time.

My experience is limited to Lycoming-powered light singles so I can't really comment on other engines, but nowhere near full power is needed for correcting an excess rate of descent on a gusty approach, so there's no real reason not to leave the carb heat hot all the way to the ground.

Certainly much better than finding you don't have any power at all when you need it, because the carb is all iced up.

[Paul_Sengupta]

Lycoming engine instructions actually says, select Carb Air Cold AFTER full power selection.

Lycoming instructions and aircraft POHs aren't always 100% in agreement!

[GrahamB]

That’s because probability of icing is a factor of both engine and installation, IMO.

@TopCat and I both have the same engine in the same airframe but housed in different cowlings, albeit with essentially the same induction system.

I have experienced significant carb icing both in the air, and on the ground (but less so, probably due to the fact that I operate from a hard surface, he is based at a grass field).

[rusty eagle]

I've had carb icing at full power climb out from a UK grass field, in January when flying an L4 Cub. I immediately pulled carb heat and after the engine revs dropped further as melted ice was drawn into the engine, full power was restored.

I now always use a carb icing probability chart when flight planning.

[A4 Pacific]

I've had carb icing at full power climb out from a UK grass field, in January when flying an L4 Cub. I immediately pulled carb heat and after the engine revs dropped further as melted ice was drawn into the engine, full power was restored.

I now always use a carb icing probability chart when flight planning.

I don’t know what engine that L4 has? I sit behind a Continental and I would never ever bother to check any “carb icing probability chart” in my flight planning. Can’t see the point. There are hardly any days when it’s not going to ice up if I give it half a chance!

That hurricane accident referred to earlier has nothing whatsoever to do with what we are discussing here. The aircraft was just very badly handled by a pilot whose ability ran out before the airspeed did..

From the AAIB report:

The tailwheel then remained off the ground until the landing gear collapsed.

The video is not clear but appears to show the elevator approximately neutral throughout. The ailerons are not in view until quite late in the sequence, when it appears into-wind aileron was applied. The rudder does not appear to be significantly deflected at any time.

I imagine it won’t matter how much airflow you have over the rudder if you don’t use it?

A pretty expensive (if very basic) error.