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QUESTION: Dear Mike

en.wikipedia.org/wiki/Landing_gear

Are the Landing gears always retractable in all airplanes ?.

i.e.

Once the airplanes takes off, the front and rear wheels are always
folded ?.
Once the airplanes wants to Land, the front and rear wheels are unfolded ?.

What are the Pros and Cons with and without having these retractable mechanism for Landing gears in airplanes ?.

Thanks & Regards,
Prashant S Akerkar

ANSWER: Hi Prashant,  
Most airplanes do have retractable landing gear,  but not all.  Many small,  single-ended airplanes have 'fixed gear',  meaning that the landing gear does not retract.

The biggest benefit to having retractable landing gear is better aerodynamics.  The plane will travel faster and use less fuel as a result of eliminating drag caused by fixed gear.

There are a few downsides to having retractable landing gear,  though. One is cost.  It is more expensive to have the mechanisms required to retract the gear.The hydraulics,  electronics,  and  other components cost more than having fixed gear.
Another downside is weight.  The added mechanical components add weight to the aircraft.  In large commercial airliners,  the increased weight and costs are  negligible,  so the added speed and fuel savings are worth a small increase in weight and additional cost.
In smaller airplanes,  the added cost and weight ARE  a factor.  When the useful loads (total weight a plane can carry,  including fuel and passengers)  are already limited,  every pound you can save is important. And since small planes are bought by individuals and not huge airlines,  every dollar counts,  too.

---------- FOLLOW-UP ----------

QUESTION: Dear Mike

Thank you.


Is it advisable for the pilot when the plane is in motion (flying) i.e. after airplane take of that in between they can also do "Wheels down" and "Wheels up" status ?.

Are there any specific advantages or disadvantages in doing Wheels down or Wheels up status when the plane is in motion i.e. running at specific speed in miles per hour ?.

Awaiting your reply,

Thanks & Regards,
Prashant S Akerkar

Answer
Hi Prashant,
I'm not exactly sure what you mean,  but I'll try to answer as best I can.  If my answer isn't what you are looking for,  feel free to follow up.

In my last answer,  I discussed how landing gear adversely affects the aerodynamics of an airplane,  when the landing gear is down.
So,  it is almost always beneficial to retract the landing gear as soon as possible after take off.  This reduces aerodynamic drag and allows the airplane to increase airspeed during the climbing phase of flight. When taking off,  the pilot wants to climb as quickly as possible to clear any obstacles and to be as high as possible in the case of an emergency.  This gives the pilot the most time possible to deal with an emergency,  mechanical failure,  or find a suitable landing spot if an emergency lading is necessary.
 There is,  however,  a period of time right after takeoff, when the pilot waits to retract the gear.  The pilot waits until the airplane has a positive rate of climb (meaning that the airplane is producing enough power to gain altitude)  and when the remaining runway  is not sufficiently long enough to land on,  in case the takeoff is aborted.
Once both of those conditions exist,  there is no longer any benefit to keeping  the landing gear extended.  In fact,  at that point,  keeping the landing gear extended is detrimental.
I hope that helps, Prashant.  if it doesn't answer the question,  or you have any other questions,  let me know.  


Mike B.  

Aviation/Flying

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Mike Burbridge

Expertise

General aviation technical, training, rules and regs., instrument flying and training for the private license, the instrument rating, and commercial license.

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I have roughly 400 hours flying time, an instrument rating, complex endorsement, and currently working on commercial license and multi-engine rating

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Aircraft Owners and Pilots Association

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