Professional Pilot, January 2016

clear ice and snow around units and also provide a heat signature for forward looking infrared systems FLIR that may be part of an Enhanced Flight Vision System EFVS LED units do not generate anywhere near the same level of heat for lumen value but may optionally be equipped with heating elements to fix these problems Not all LED airport lighting systems may opt for heating particularly at airports where snow and ice are not an issue Visual slope indicator systems are being replaced by PAPIs Perhaps less understood is the role and status for visual slope indicator systems such as PAPIs VASIs or PVASIs Visual Approach Slope Indicator and Pulsating Visual Approach Slope Indicator systems are older units which are being superseded by Precision Approach Path Indicators when replacement is necessary All 3 systems work well but PAPIs are simpler and generally less expensive The FAAs opening statement concerning PAPI systems is they are primarily intended for use in VMC Regardless the FAA recognizes that PAPIs are part of the runway environment and may be used to descend below DH or MDA to 100 ft above the Threshold Crossing Height TCH on an instrument approach FAR 91175 In ideal weather conditions PAPIs may be visible as far out as 20 miles PAPI systems that are newly installed at airports must be flightchecked by the FAA before use as well as every subsequent FAA flightcheck PAPI systems may be used to mitigate 72 PROFESSIONAL PILOT January 2016 Thales TopMax wearable mini HUD is a derivative from a military system that has been tested in combat aircraft where cockpit space restricts the use of a more normal HUD a minor obstruction to the protected approach airspace for a runway in certain specific circumstances PAPIs provide obstruction clearance for a wedge that is 10 degrees wide either side of the runway centerline out to a distance of 4 miles from the units Any guidance provided on a visual base leg when more than this 10 degree angle to the runway should be ignored as it may not guarantee obstacle clearance Problem units that are too widely visible may require vanes to limit the width of view The recommendation is to only use the PAPI for vertical guidance when established on final and within 4 miles Each light housing unit in a 2 or 4 element PAPI is set when installed and reset as often as necessary for each lamp to project the correct unique angle for that unit Each unit separately has a tilt switch in case it is misaligned mowing or clearing snow from around the unit If one unit lowers more than 1 4 degree or raises more than 1 2 degree all units will time out If there is still a misalignment when the unit times in again the PAPIs will deactivate PAPI units are placed so the on glidepath indication white white red red when you are over the end of the runway is for a TCH that matches the cockpitto landing gear height of the group of aircraft expected to use the runway This TCH varies from 40 ft AGL for GA small commuter and corporate aircraft to 75 ft AGL for heavier aircraft such as the Boeing 767 and other airline aircraft The display you see on the PAPIs when crossing the runway threshold on landing thus may not coincide with your electronic glideslope indication or your general runway visual clues if you operate in a different cockpit to landing gear height group than those the PAPIs are set for Enhanced flight vision systems EFVS is defined as an electronic means to provide a display of the forward external scene topography the natural or manmade features of a place or region especially in a way to show their relative positions and elevation through the use of imaging sensors such as a FLIR millimeter wave radiometry millimeter wave radar or low light level image intensifying Multiple sensors integrate and present the pilot a single view currently via a head up display HUD The FAA has re opened the notice of proposed rulemaking FAA 2013 0485 concerning EFVS with the following summary This rulemaking would permit operators to use an EFVS in lieu of natural vision to continue descending from 100 feet height above runway touchdown LED threshold lamp All aviation LED lighting units are made up of multiple LED elements most often of several slightly different hues to create an overall color frequency similar to incandescent units Elbit SkyLens is a suggested substitute for a normal HUD wherein the pilot has a head harness allowing the wearing of eyeglasses and also the use a standard headset