Impact of GNSS signal loss on aircraft operations - Be Prepared

The power of the GPS signal “is comparable to the power emitted by a 60-watt light bulb located more than 20,000 km [12,000 mi.] away from the surface of the earth; this means the signal could easily be disturbed by any ground source located near an aircraft and emitting in the GPS L1 frequency,” Airbus experts in operations, navigation and security say in a company publication focusing on safety.

Interference can cause the loss of GNSS position and timing. In that instance, the Flight Management System (FMS) will revert to the onboard inertial reference system (IRS) and ground-based navigation aids, such as DME and VOR (distance measuring equipment and VHF omnidirectional range). “A loss of GNSS inputs does not lead to a map shift or an erroneous position computation by the FMS. In the case of a loss of GPS signal, the FMS switches from the mixed GPS/IRS position to an IRS-DME/DME position or IRS-VOR/DME or pure IRS, in order of priority,” the experts explain.

How to handle these events in the daily aircraft operations

When GNSS signals from satellite constellation are lost or degraded by interferences, depending on the duration, aircraft capabilities can be maintained, limited or lost during the flight. 

Cockpit effects that can be observed by the flight crew during total loss of GNSS signal.

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Maintenance recommendations to be considered during post-flight analysis after GNSS loss event.

 A320, A330, A340, A380 and A350 aircrafts

 GPS output sent to the IRS which sends a “hybridized” position to the FMS).

These aircraft are fitted with two MMRs, three ADIRUs and two (A320/A330/A340/A380) or three (A350) FMS to compute the aircraft position. 

In case GPS data is lost due to GNSS RFI affecting both MMRs, the aircraft position source will switch to pure IRS and will enter into the so called coasting mode. If the integrity of GPIRS data is degraded enough then the position source will switch to other radio navigation based solution (from FMS) according to the availability of DME and VOR. If Navaids are not available, the aircraft position solution will switch to IRS only.

CAE Hurry Up Production of Boeing 737 Max Flight Simulators

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Long a manufacturer of full-flight simulators, CAE also runs the world’s largest training network for civil aviation pilots, with about 300 devices deployed at company-run facilities in cities such as Abu Dhabi, Kuala Lumpur and London. CAE says its 2,000 instructors train more than 135,000 pilots every year.

Airlines that bought the MAX have had to cancel flights while the global fleet remains grounded.

If only computer-based training were required for renewed 737 MAX commercial flying, Boeing’s largest customer Southwest Airlines Co had said it would take one to two months to prepare its more than 9,500 pilots on the updates.

Southwest had not been part of Boeing’s recent discussions on pilot training recommendations and could not provide additional cost or timing estimates before there was specific guidance, spokeswoman Brandy King said.

Southwest has three MAX simulators in various stages of FAA certification and expects three more later this year.

American Airlines Group Inc and United Airlines each have one MAX simulator.

Not many MAX simulators exist and it was unclear if training could be performed on the 737 NG simulator that 737 pilots have used until now. As of December, Toronto-based manufacturer CAE Inc had delivered 23 MAX full-flight simulators, a spokeswoman said.

The FAA said on Tuesday it will consider Boeing’s recommendations during training evaluations of U.S. and international flight crew alongside regulators from Canada, Europe and Brazil.

Canada’s Transport Minister Marc Garneau, who has leaned toward mandatory simulator training for Canadian 737 MAX operators, said in a statement that Boeing’s signaling the importance of such training was “encouraging.”

Boeing 737-800 MAX training on Tablet before Accidents Criticized

Boeing’s proposal to skip flight simulator training for pilots when its grounded fleet of 737 Maxes is cleared to resume service is not an innocent one. Much of the criticism the company has faced is that the original training for the Max 8 for pilots who had flown previous versions of the 737 aircraft was an hour-long course on a tablet. This was part of a scheme by the company to reduce the cost of the new plane for airlines and minimize the time needed to get it into the air. Corners were cut in order to beat back a challenge from Boeing’s European-based rival Airbus, whose new short- and mid-range commercial jet was threatening to capture lucrative markets long dominated by the US giant as well as the rapidly growing Asian market.

PORTUGUÊS

A proposta da BOEING de pular o treinamento de simulador de voo para pilotos quando sua frota  de 737 Maxes no solo for liberada para retomar o serviço não é inocente. Grande parte das críticas que a empresa tem enferentado é que o treinamento original para o Max 8 para pilotos que haviam voado versões anteriores da aeronave 737 era um curso de uma hora em um tablet. Isso fazia parte de um esquema da empresa para reduzir o custo do novo avião para as companhias aéreas e minimizar o tempo necessário para obtê-lo no ar. As arestas foram aparadas para vencer um desafio da rival europeia AIRBUS, cuja nova aeronave comercial de curto e médio alcance ameaçava capturar mercados lucrativos há muito dominados pelo gigante dos EUA, bem como pelo mercado asiático em rápido crescimento.