FAA mandates all altimeters be updated to prevent 5G interference

Operators in the USA will need to update all their altimeters, some 58,500 units, under a new FAA rule.

US airlines and foreign carriers flying to the USA must update radio altimeters on all their aircraft by the end of 2030 under a new Federal Aviation Administration (FAA) rule intended to prevent interference from 5G cellular signals.

The FAA’s newly issued rule requires non-airline operators to update all altimeters on their aircraft also, but they will have nearly four more years to comply. The agency had proposed the rule in January but had not initially specified deadlines.

The move comes as the US Federal Communications Commission prepares to auction to cellular companies a new slice of radio bandwidth in the 3.98-4.2GHz range.

But that bandwidth, which cellular firms intend to use to expand their 5G networks, sits close to the 4.2-4.4GHz range used by aircraft altimeters. The FAA says the proximity of the ranges means 5G signals could interfere with altimeters, causing inaccurate readings.

The agency’s new rule therefore requires that aircraft be equipped only with “interference tolerant” altimeters.

“These new radio altimeters must withstand interference from wireless signals in neighbouring spectrum bands and continue to provide accurate altitude readings to both pilots and integrated aircraft safety systems,” the FAA says.

The rule sets a 30 December 2030 deadline by which airlines must equip their jets with upgraded devices. That deadline applies to aircraft with 30 seats or more, or with payload capacities exceeding 7,500lb (3,402kg), including aircraft operated by US and non-US airlines.

All other aircraft – including charters, commuters, general aviation types – must have updated altimeters by 31 October 2034.

The rule is sweeping, applying to an estimated 58,500 altimeters on 40,700 aircraft.

US airlines alone will need to update 17,000 units on nearly 8,000 aircraft at a cost of $80,000-120,000 per altimeter, for an estimated $1.5-2.2 billion total expense, the rule says.

Non-airline US operators will need to update another roughly 30,000 altimeters – a $2.4-3.4 billion hit.

The expense for all US operators, however, will be paid via “transfers” from cellular companies using the new networks, the FAA says.

Cellular firms will not, however, pay for foreign carriers to update their altimeters, though “some may be able to reduce their total costs by only replacing [altimeters] in a subsection of aircraft designated for US operations”, the rule says.

The FAA puts the entire cost of the replacements across US and foreign operators at $4.8-7.1 billion.