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Question
QUESTION: Dear Kevin

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: Some light aircraft do not have retractable landing gear.  Larger aircraft, especially commercial aircraft have retractable landing gear to reduce drag and decrease operating cost.  Landing gear cause drag which needs to be overcome by increase power/ thrust, generating thrust cost fuel.  

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

QUESTION: Dear Kevin

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
As mentioned previously landing gear extended in flight cause drag.  So to maintain any desired speed with landing gear down will require more thrust therefore more fuel and increased cost.  The advantage to having a fixed landing gear that doesn't retract is achieved if the cost of installing a retractable gear system is greater than the disadvantage of the drag created.  This is why some light aircraft have fixed landing gear.  

For large aircraft, operating with gear extended reduces the maximum operating speed and altitude.  

Your questions suggest that reading a few aerodynamics books like "Handling the Big Jets" would be helpful.

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Kevin Parker

Expertise

I will do my best to answer any question related to my experience. If I don't know, I promise to help you find the answer. Every question deserves an answer.

Experience

I have 30 years experience in Commercial Type Rating training, program development, human factors, instructor training, flight simulation and flying large aircraft in general. Operated L188, DC8, B747, B757, A320, A330 and A340 aircraft. Involved in cockpit design, flight testing and type certification.

Education/Credentials
Aviation college, military flight instructor, ATPL, check airman, maintenance test pilot, Simulator Test and Evaluation Pilot, Production Chief Pilot

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