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Gremline Flight Safety Report: Crosswind Landings / Bowled Over by Boeing

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Text Box: crosswind landings / bowled over by boeing

the gremline digest —  crosswind landings / bowled over by boeing

Crosswind Landings in Light Aircraft

It is not unusual for crosswind landings in light aircraft to end up with a trip off the runway or even a bent aircraft lying at a large angle to the intended landing direction.

 

 Each type of aircraft will exhibit its own peculiar behaviour when landing in a crosswind, so anything written here is a generalisation and may or may not apply to your aircraft. As with all landings, a good crosswind landing begins with a good approach. It is no good flying a ragged approach and hoping to sort it out just before touchdown. If you are uncomfortable anywhere on the approach then your best bet is to go around early and set yourself up for another, unhurried, approach and landing that you have had time to plan carefully. How you fly the approach will depend on your training, your level of experience, your currency and your aircraft type. There will probably always be discussion about the merits of the ‘wing down’ approach versus the ‘crabbing’ approach. I don’t intend to preach the merits of either type of approach. If pressed, I would probably side with the ‘don’t know’ voters and admit that I probably use a mixture of both techniques depending on the conditions and the aircraft being flown. This may be a product of some sixty years flying a good few different aircraft types.

 

 

 There are a few words of general advice for those not experienced with dealing with a strong crosswind. First, avoid landing in a strong crosswind until you are really happy handling a gentle crosswind. If the forecast predicts a crosswind component approaching the maximum for your aircraft type perhaps it would be wiser to wait for another day. If you find yourself approaching an airfield that has a crosswind close to your maximum, then consider the possibility of using another runway with less crosswind component. It is not absolutely essential to land on the runway in use if there is another runway available that has a lesser crosswind. Ask Air Traffic. That’s what they are there for! A second option that may be considered is a diversion to a nearby airfield that has a landing direction available that is more into wind.

      I have mentioned ‘maximum crosswind’ for your aircraft several times above. You need to give very careful thought to exactly what is the ‘maximum crosswind’ for you aircraft. If there is a figure quoted in the Limitations part of your Owners Handbook or whatever your book of advice is called, then be certain that figure IS NOT a figure you can take as the maximum crosswind component you can handle in your aircraft. That figure is almost certainly the figure beyond which a highly skilled test pilot could not control the brand new aircraft type in conditions of a steady crosswind component. No gusts, no turbulence from nearby buildings or trees, no undulating grass airfield, no nervous passengers peering over your shoulder and no very large bill to pay if it all goes pear-shaped. I can’t tell you what your maximum crosswind is, but I CAN tell you that it’s less than the figure in the Owners Handbook. You are the limiting factor, not the aircraft.

 

 

When you are planning a landing in a strong crosswind remember to think about what you are going to do AFTER the successful touchdown and after the landing roll has ended. The strong wind will still be there after you have stopped. It would be silly to heave a sigh of relief after the landing only to be flipped upside down by a gust of wind. Do you need wing walkers to assist while clearing the runway? Which way are you going to turn after you stop? What difference does it make if your aircraft has a tailwheel? Do high wings react differently to low wings? Has your aircraft got a particularly light wing loading? How do you use the ailerons when taxiing crosswind? How do you use the elevator when taxiing downwind? Is it better to stay in the aircraft while waiting for assistance to arrive? Wouldn’t it have been better to leave the aircraft in the hangar until another day?

      There is one piece of advice that applies to landing any aircraft type in a crosswind. Avoid any tailwind component. It may not be immediately obvious why a tailwind component in the crosswind makes control of the aircraft much more difficult during landing. Firstly, if any swing into wind is allowed to develop then the swing will tend to increase because, as the nose swings into wind the crosswind component INCREASES as the wind angle approaches ninety degrees. This will become apparent as the aircraft slows after touchdown. This is opposite to the effect if the crosswind is less than ninety degrees, when any into wind swing DECREASES the crosswind component as the wind angle decreases. Another, often forgotten, factor is that with any tailwind component of the crosswind the inertia of the aircraft is significantly increased. Inertia is proportional to the SQUARE of the groundspeed. In the same situation the effectiveness of the fin and rudder, being a function of airspeed, does not increase. These factors affect all aircraft types but are particularly important to understand when landing a tailwheel type. So, a landing in a crosswind that has any tailwind component is much more difficult to control and is much more likely to go wrong. The safer option would be to land in the opposite direction to face a crosswind of less than ninety degrees and to avoid one of more than ninety degrees.

      The advice from my Royal Canadian Air Force instructor during my ab initio training on Harvards still applies. “A landing is not complete until the wheels have stopped turning.” Even then, you may still face problems taxiing in a strong wind. Plan ahead and live long.

 

 

Bowled Over By Boeing

Nature is not the only potential source of hazardous crosswinds! A young student pilot was following ATC instructions as he taxied his Cessna 150 towards the active runway of a UK International Airport.

 

The initial clearance was to taxi to Holding Point S1 while a Boeing 747 taxied to Holding Point R1. Holding Point R1 is between the secondary runway and a taxiway parallel to that runway. Thus the Boeing 747 was holding with its nose pointing towards the secondary runway and the tail pointing directly across the parallel taxiway. The Boeing departure was delayed as it waited for oceanic clearance, so ATC cleared the Cessna to pass behind the 747, having requested the Boeing to maintain idle engine power as the light aircraft crossed behind it. This was acknowledged by the Boeing 747. As the student taxied behind the Boeing he felt the aircraft shaking violently and it was then blown up onto its left wing and spun clockwise through 180° before the right wing and propeller struck the ground. The student was unhurt.
      Transport Canada Aeronautical Information Publication (AIP) dated 15 March 1984 indicates that the danger area of a ‘Jumbo Jet’ size aircraft on the ground extends to 600 feet behind the tail of the aircraft. In this accident the Cessna passed directly behind the tail of the Boeing 747. There was a similar accident to a Cessna 172 when it taxied through the jet efflux of a Boeing 777 on the ground. In that case the Cessna passed 102.5 metres behind the Boeing 777.

 


There may still be a lack of appreciation of the hazards of engine efflux on the ground by aircraft crews and ATC personnel. All pilots, particularly those of light aircraft, should avoid taxiing through the engine efflux of nearby aircraft on the ground.
      This report is closely based on AAIB Report EW/G2005/01/09, which source is gratefully acknowledged.

 

 

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