T45 Flight Deck product header image


Landing Period Designator (Quiescent Period Prediction) – Helicopter and UAV Landing Aid System

Landing Period Designator unit from Aeronautical & General Instruments (AGI) Ltd


Aeronautical & General Instruments Limited (AGI) have over 20 years experience and proven success with the design and manufacture of solid state Military specification ship-based electronic equipment and Visual Landing Aids, with the LPD – Landing Period Designator (Quiescent Period Predictor) being the latest addition to the product range.


The Landing Period Designator (LPD) is a solid state landing aid system that is designed to reduce air and ship crew workload associated with aircraft launch and recovery operations on moving ship platforms by providing a clear, real time visual indication to the pilot of the optimum time to take off and land safely (i.e. the quiescent deck motion period or quiescent period prediction, QPP). In addition to reducing the risk of aircraft undercarriage or structural damage, LPD offers improved operational safety by minimising over deck hover time and provides increased tactical flexibility by expanding the aircraft operating and landing envelopes, regardless of the sea condition or the time of day or night.

LPD can also be incorporated directly into Unmanned Air Vehicle (UAV) control systems to ensure that automated UAV launch and recovery occurs during the most optimum and safest time period possible.

LPD works alongside the established aircraft landing procedures and after being extensively trialled by Navies worldwide, has been proved to offer a substantial increase in safety for ship board launch and recovery routines for both manned and unmanned air vehicles.

LPD supplies the real-time information concerning ship’s motion as a function of aircraft operational limits and measurement of ship’s pitch, roll, surge, sway, yaw and heave to the pilot and crew via a hangar mounted Pilot Information Display (PID), which indicates with clear symbols the current deck energy and the optimum opportunity to take off and/or land the aircraft.


The principle of LPD is based on the rate at which a vessel can displace fluid due to hydrodynamic forces. LPD supplies real-time information concerning ship’s motion as a function of aircraft operational limits and measurement of ship’s six degrees of motion from directly underneath the vessel’s flight deck. This information is processed by the system’s LPD algorithm and expressed as the ship’s Energy Index (EI), which relates ship’s motion to an EI scale. An EI of 0-4 indicates a safe quiescent deck, an EI of 4-10 indicates a caution deck and an EI of above 10 signifies an unsafe, ‘out of limits’ deck.

Each deck status phase has a corresponding EI symbol for display to both the crew and pilot, with the real time EI information either transmitted instantaneously to the PID on the flight deck for manned air vehicle operations, or used to aid the automated launch and recovery of a UAV where the LPD software is integrated into the UAV control system


  • Industry leading and proven technology
  • Mounted underneath flight deck to provide the best possible heave measurement and avoid possible errors from long lever arms and ship
  • hull torsion
  • Real-time motion data transmitted directly to the LPD console


  • Based on AGI’s proven MFCR hardware
  • embedded LPD software to calculate and display the Energy Index (EI) and Ship Motion information to the Flight Control crew
  • Transmits the real-time EI data to the flight deck mounted Pilot Information Display
  • Status screen provides a Data Integrity summary and System Event log


  • Mounted in an elevated position above the flight deck to ensure maximum visibility to the pilot whilst in the hover position
  • Utilises high brightness LED’s to convey the real time Energy Index symbol to the pilot
  • Optional additional AGI Wave-Off Light to ensure 360° visibility around the vessel


Landing Period Designator (LPD) datasheet

Helicopter Landing Aid

LPD datasheet


Complete Naval product range

AGI NTD 16pp broch


T: +44 (0) 1202 685661

E: via our contact form