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Electronics/Retractable mechanism for Landing gear in airplanes.

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QUESTION: Dear ZZ

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 ?.

Once the commercial airplane takes off by what time the front and rear wheels are folded ?. i.e. after 1/2 min, 1 min, 5 min, 10 min etc ....

Once the commercial airplane has to land before what time the front and rear wheels are unfolded ?. i.e. within 1/2 min, 1 min, 5 min, 10 min, 30 min etc ....

Are both these timings critical i.e. After plane take of and Before Landing and are these timings fixed globally as part of airplane operations ?.

Thanks & Regards,
Prashant S Akerkar

ANSWER: Once again, this is not a question for Electronics. I am not an expert in aviation or airplane design.

From actually flying on many, many different types of aircraft in my lifetime I can tell you there are aircraft both with and without retracting landing and takeoff gear.

The virtue of sucking the wheels up into the fuselage is lower air drag, better efficiency and fuel usage.  At high speeds the friction caused by wheels out can be very significant.

But, it adds cost and complexity to the design of the aircraft.  And, it takes space inside the fuselage to hide them; which, in some small aircraft there simply is not room for them.

Most jet powered aircraft will have the wheels brot in due to the great speeds they can achieve.  Most small private 2, 3, 4 and 8 passenger prop planes will likely not have retractable wheels.

Timing is somewhat critical as the pilot must be totally clear that the plane is airborne.  The wheels coming up as early as possible will aid in getting to flight elevation quickly and efficiently.  I do not know the timing.  In modern commercial passenger planes it may be done automatically by computer program; I don't know.

Good Luck.



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

QUESTION: Dear ZZ

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
I have no idea regarding this question.

The purpose, obviously, of the wheels are to move about when on the ground.  They have no purpose and are counterproductive to be open when in flight.  They cause expensive drag on the vessel when out in the open.  The pilot would always want the wheels up when in flight.

cheers.

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ZZ

Expertise

Electronics questions about AC, DC and digital theory.

Experience

Graduate electrical engineer with over 40 years in electronic design, manufacturing, project organization and patent review. Experience in fields of industrial and consumer electronics (audio, video, acoustics, etc.)

Organizations
IEEE (Institute of Electrical and Electronics Engineers); Senior Life member AES (Audio Engineering Society), Fellow Life member

Education/Credentials
BSEE University of North Dakota

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