Wind, ,and take-offand landing 

Nick: Hi, there. 5 Minutes with AOPA-China,Episode 49.Beijing has always been a windycityin China.This weekif you are in Beijing, you know what I mean. Most residents in Beijing must have seen thepower of strong winds this Monday. And51 out of 1,561 scheduledflights were canceled at Beijing Capital International Airportby 6 pmlast Sunday. Many airplanes whichhad been intended to land in PEK had to fly to the alternate airports.Of course,this caused inconveniences. Many people had to reschedule their trips and timeare wasted.There wasanextreme example. The planewas hundreds of feet above the runway, still it went aroundand land in an alternate airport.

Nick:How doesWind affect aircraft takeoff and landing?Today wehave our friend, Captain Kingsley, a commercial jet pilot and helicopter instructor from New Zealand.Kingsley,now I’m all ears.

Kingsley Captain:Aircraft are designed totakesoff and land into a headwind as thisreduces the distance they require to get airborne or distance need to bring theaircraft to a stop.The reason behind this strategy is ofcourse toincrease safetyas much as possible. If you watch nature, it isvery clever. If you see birds fly, they willinstinctivelytake off and land into wind. Let me give you a morespecific aviation example. IFor example, ifan aircraft is standing still on the runway, and has a headwind component of20kts, that’s 20kts of air flowing over the wing and therefore giving theaircraft an airspeed of 20kts, even though it’s not moving. If it has a takeoff speed of 140kts, the aircraft’s ground speed would only need to be 120ktsto get airborne because it already has 20kts of airspeed from the wind.

On the other hand, crosswinds and tailwindsare more difficult, and therefore aircraft have maximum limits for both,depending on the plane, the airport and the conditions on the runway. If windspeedsexceedsthose limits, thepilotwillplane willnot attempttakeoffabandon takeoffor landing.

Nick: Can you tell us more about themaximum wind limits for a commercial jet aircraft?

KingsleyCaptain:Verygood question. So let’s choose a well-known aircraft as an example----Forexample,on a dry runway, aBoeing 737-800, ithas a maximum allowable crosswind component of approximately 33ktswhen ituses a dry runway to take of. For taking off on a wet runway it’sabout 27kts. The actual figure might be slightly above or below this becausethe airline can choose to set its own more restrictive value if it wishes, forsafety control. If the cross wind component was greater than this,the aircraft might have an option to choose another runway which is more intowind, but in the case of a single runway airport, it wouldn’t be able todepart.

As for landing, the Boeing 737-800crosswind limitation is the same as take-off, 33kts. On a wet runway thisagain reduces to a maximum of 30kts.

The maximum tailwind component for take offand landing is usually between 10-15kts, but the actual figure that can be usedmay be affected by runway length, aircraft weight etc.

In the event of a contaminated runway, boththe maximum allowable crosswind / tailwind limits reduce, depending on the typeand depth of the contaminant. Actually most airlines do not allow a tailwindtakeoff on a contaminated runway. 

Moreover, there is anotherkind of limits:door limits.It refersto the limits on when the cargo and passenger doors can be opened. If the windis more than about 45kts, it isn’t deemed safe to open the doors.

Nick: What hazard may be generated if thepilot makes inadvisable landing in strong winds?

KingsleyCaptain:The toweralways advises the landing conditions on the airport. So we aspilots can consider the viability to land safely.Landingin a strong, gusty crosswind is challengingeven for more experiencedsenior pilots.Pilots had better not take this risk if it’s notadvisable to land., especially when there are two hundred passengerson Thoughboard.ThoughTthis skill isone that all professional pilots must master early in their careers, judgmentis essential to determine when the conditions are too severe to safely land.Good judgment keeps it from being dangerous. Going around or landing at thealternate airport is safer than landing in the unfriendly wind.Flyingexperience,sound knowledge of the aircraft and good judgementof the conditions is what keep the operation safe. You all notethat Imention safety a lot. This is obviously the primary objectivefor allpilots.

Nick: Thank you, Captain.So dearpassengers,whenyourourflighthappens tomeetsstrong wind, be calm and patient staying grounded since the decision is made inaccordance with SOP which ensures your safety.I am surewe are in good hands. Safe journey.

If you are a pilot to be, you will learn all aboutit during your ground schoolsection.

Do you find this topic interesting? What’s yourinputon this?Write ustoWhat’s your opinion on today’s topic? Wear yourheart on your sleeve in the comment area or send emails [email protected] in the 5PMAviationQuiz.That bringsus to the end of today’s 5 Minutes with AOPA-China.You can alsofind us on Wechat, Facebook, Twitter, Ximalaya or any podcast platform. Search “5Minutes with AOPA-China”, and rate us if you like us. So much for today.there yougo.

Bye for now.

Words and Expressions

1.Headwind逆风

2.Tailwind顺风

3.Crosswind侧风

4.Knot节（单位）

5.SOP:standardoperating procedure标准运行程序