Definition
A backup method for lowering the landing gear when the normal extension system has failed. Depending on the aircraft, this may involve a hand crank, a manual release that allows the gear to free-fall and lock down under gravity and airflow, a pneumatic blowdown bottle, or an emergency hydraulic pump. The specific procedure is published in the Pilot's Operating Handbook (POH) or Airplane Flight Manual (AFM) for that aircraft.
Plain English
A backup way to put the landing gear down when the normal system stops working. Each aircraft has its own backup procedure, written in its handbook.
Context Anchor
Encountered in emergency procedures, especially when an engine failure or system problem may prevent normal landing gear or flap extension.
Derivation
Alternate' here means 'a second option used when the first one fails,' not 'taking turns.' 'Means of extension' simply means 'a way of putting the gear down.' Together: a backup way to lower the gear.
Why Pilots Care
Allows a pilot to land with the gear extended instead of performing a gear-up landing, reducing aircraft damage and personal injury risk.
Intuition Check
“Alternate” does not mean a different destination or a different plan for the whole flight here. It means the backup method for extending the equipment when the normal method is not available.
Example Sentence 1
When the gear handle was selected down and no green lights illuminated, the pilot referred to the POH and used the alternate means of extension to lower the gear manually.
Example Sentence 2
The alternate means of extension allowed the airplane to land safely on the runway after the primary system malfunctioned.