Ground Proximity Warning Systems (GPWS) refer to the safety systems installed on aircraft to generate mandatory response Warnings and advisory Alerts to prevent potential terrain accidents. Threat crash detection triggers visual and aural warnings in the cockpit to alert the pilots and the rest of the crew to take prompt action.
While advancements and technology mean new systems are being developed rapidly with additional safety features, the current Ground Proximity Warning Systems are classified into basic and enhanced systems.
If you’re a pilot looking to switch to regional airlines, a good way to familiarize yourself with different controls, protocols, and systems is to enroll in an accredited aviation pilot training program.
Momentum Flight Training offers top-of-the-line aircraft simulator training on full-service AATD that replicates the systems in the Canadair Regional Jet 200, 550, 700, and 900 American airlines to enable pilots to gain confidence in a realistic flying regional aircraft environment.
While their instructor-led aviation pilot training programs help polish skills and knowledge related to Flight Management Systems (FMS), Electronic Flight Instrumentation Systems (EFIS), Electronic Flight Instrumentation Systems (EFIS), and Engine Indication and Crew Alerting Systems (EICAS), this guide focuses on Ground Proximity Warning Systems.
What’s a Basic GPWS System?
The basic GPWS functions to measure the height of the aircraft and the rate at which it changes. It utilizes ‘Rad Alts’ or radio altimeters that transmit radio waves underneath the jet and measure the time taken for them to be reflected back to the plane. This helps get the ‘radio altitude’ of the aircraft, a measure of its height over the ground.
The aircraft’s radio altitude is combined with its ILS glide slope and landing gear or flap configurations to generate warning and caution call-outs. Typically, Ground Proximity Warning Systems have five basic modes that are active up to the radio altitude of 2500 feet above the ground.
The modes include everything from Excessive Rate of Descent (Mode 1) to Excessive Terrain Closure Rate (Mode 2), Altitude Loss following a go-around or takeoff (Mode 3), Insufficient Terrain Clearance (Mode 4), and Excessive Descent below Glide Slope (Mode 5).
However, the call-out cautions and warnings generally differ depending on many factors, ranging from the type of aircraft to different systems installed in the same model. Moreover, the basic GPWS modes don’t have any knowledge about the aircraft’s location. They simply trigger when the set parameters exceed.
Essentially, all basic GPWS modes look down instead of looking ahead. This means that if an aircraft is supposedly flying over flat-leveled ground, the rad alts won’t detect any change or trigger any alerts until the plane crashes into a mountain or cliff. This problem doesn’t exist in EGPWS—Enhanced Ground Proximity Warning Systems.
The system overlays the computed position of an aircraft with the database of known obstacles, buildings, water bodies, and terrains to create warning and caution ‘envelopes’ ahead of time to promptly trigger relevant warnings and call-outs.
Additionally, EGPWS also provides a warning for approaches below minimum safe altitude and potential runway intrusions. The safety device proactively helps pilots avert a number of accidents.
The latest EGPWS systems, or what the Federal Aviation Administration (FAA) likes to call Terrain Awareness Warning Systems (TAWS), are equippe with many more advanced features.
These predictive systems come with computer models of the performance of aircraft that it used to create warning and caution envelopes that await the jet, including its climbing ability. It utilized databases to display hazards and operates by inhibiting the basic Mode 2 of GPWS. The
Excessive Terrain Closure Rate is re-activate when the predictive EGPWS detects a failure or significant discrepancies between the T2CAS altitude and rad alt height. The crew will be alerte through EICAS or ECAM warnings if problems occur with the EGPWS.
Moreover, pilots receive GPWS warnings when a dangerous flight path is detecte by the system. But if the crew doesn’t react to the flashy noises and lights denoting the caution, warnings replace these call-outs.
Even if you’re an experienced pilot, regional airlines are no easy feat without proper training. 1-day, 3-day, and 5-day instructor-led aviation pilot training programs by Momentum Flight Training are great for helping even experienced pilots to exercise sound judgment during emergencies.
Their CRJ simulator comprises switches and knobs that simulate a realistic feel of the flight deck environment. The immersive display and experienced instructors help aspiring regional pilots enjoy a powerful learning experience and gain confidence to navigate different situations and follow procedures common in many aircraft.
Pilots with a commercial or CFI rating looking to transition into a first-officer role in a CJR 200, 550, 700, and 900 American airlines can reach out to the training institution for more information. Call  427-5876 to speak with one of their experienced instructors.
About the Author
The author of this post boasts an aviation career that spans two decades. She has cumulated 12,000 hours of flight time and worked as a designated FAA examiner after completing captaincy at a regional airline.