There are usually six primary instruments on an aircraft's main flying panel which enable the pilot to determine his aircraft’s position in the sky.
They consist of the Airspeed Indicator, Attitude Indicator, Heading Indicator and Turn Coordinator. The final instrument in the aircraft's ‘six-pack’ is the Vertical Speed or Climb Indicator.
Vertical airspeed is the rate at which an airplane ascends or descends. Differing from ground speed, it displays the aircraft’s rate of climb by tracking the airplane’s vertical airspeed, and the rate of descent, or sink rate, which indicates how quickly the airplane is descending.
Displayed as feet per minute, or FPM, like many of the six-pack’ instruments, the Rate of Climb Indicator is connected to the aircraft’s pitot-static system which is often seen as an ‘L’ shaped tube protruding from the airframe or wing and measures air velocity at right angles to the direction of airflow.
Through a series of rods, gears and a flexible diaphragm, the airflow entering the port informs the vertical speed indicator display, which is traditionally a needle dial. Modern cockpits might feature a digital Vertical Speed Indicator.
Displaying the rate at which the airplane is moving along the vertical axis, the larger the pressure differential between the casing of the mechanism and the diaphragm, the more dramatic the movement of the needle.
When an airplane is in level flight, an opening within the diaphragm called the ‘ calibrated leak’ bleeds off the air within. This then resets the Vertical Speed Indicator to zero until the aircraft climbs or descends again.
In powered flight, the pilot makes frequent use of the instrument to ascertain that level flight is being maintained, especially during turning manoeuvres.
Pilots of older aircraft might notice that when the needle on the vertical speed indicator starts to move, it might not give precise information about how quickly the airplane is rising or dropping. This is what is known as a “trend.” However, once the diaphragm, mechanism, and data relay are caught up with what is taking place in air pressure differentials, the Vertical Speed Indicator quickly stabilises, and the actual rate becomes available.
The gap between seeing the trend and knowing the actual rate can last anywhere between six to nine-seconds Small changes which are made slowly usually show up more quickly on a traditional Vertical Speed Indicator, whilst sudden shifts in pitch can result in lags even longer than nine-seconds.
In some situations and in some aircraft, this can cost precious decision-making time and cause a pilot to assume that they have failed to pitch the airplane correctly, and to then overcorrect. Pilots who are struggling with a lagging Vertical Speed Indicator are said to be “chasing the needle.”
More modern aircraft feature instantaneous Vertical Speed Indicators which incorporate small accelerator actuated pumps in tandem with air flow sent from the pitot tube to provide the pilot with instant vertical speed information rather than waiting for the more traditional pitot-static system to catch up.
This Kelvin Hughes Mk. 3(P) Vertical Speed Indicator is of the traditional design and was installed in the Folland Gnat which had a vertical climb ability of 20,000 ft per min to its operational ceiling of 48,000 ft.
With its undamaged bakelite case and clear, scratch-free glass face, this Kelvin Hughes Mk. 3(P) Vertical Speed Indicator, presents an amazing opportunity to secure a rare piece of aviation history from an operational Folland Gnat.
Mounted on a stylish 100yr old Mango Wood Display Stand with engraved plaque and a highly detailed 1/72 or 1/48 scale model of this British high-speed military trainer and acrobatic aircrfat perched above, on its magnetic display arm and detailed Fact Sheet, it’s an ideal gift for any aviation enthusiast.
This Folland Gnat Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of instrument in aircraft cockpit.
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Your Folland Gnat Red Arrow, Kelvin Hughes Mk. 3(P) Vertical Speed Indicator, Original Recovery Curios Warbird Collectable includes:
- Highly detailed hand-built and airbrushed 1/72 plastic scale model of the aircraft or upgraded 1/48 scale model*
- Original Warbird instrument
- Hand-crafted and beautifully finished 100yr, Far North Queensland Mango Wood display stand
- Detailed, 2-sided, printed and laminated Instrument Fact Sheet detailing aircraft and instrument
- Removable Magnetic Display Arm
* Upgrade to a super detailed 1/48 scale model for only $35
The heavily detailed scale model is available with wheels & flaps up or down and cockpit open or closed. Upon order placement you will receive an email asking for your preferred configuration.
Your complete Recovery Curios Original Instrument Collectable is securely packed and delivery normally takes between 3 - 4 weeks approx.
Did you fly, crew or maintain a Folland Gnat or have a friend, colleague or family member who did? Check out our PERSONALISED ORIGINAL INSTRUMENT COLLECTABLE OPTION here.