'If the airlines are not given a clear deadline to change the altimeters by the DGCA, why should they do it voluntarily?'
'It means that the aircraft will be grounded for a while and lose money.'
Telcos are pushing the Directorate General of Civil Aviation to impose a sunset clause within which airlines have to mandatorily replace their old altimeters with the latest one so that 5G spectrum airwave radiation in airports does not interfere with an aircraft's instruments.
The DGCA had mandated a complete blackout of 5G services in airports across the country and areas within 2.1 kilometres radius due to safety concerns.
To deal with this contentious issue, a meeting was held between stakeholders and the civil aviation regulator last month.
The telcos have informed the DGCA that representatives of Boeing and Airbus have shared details of what they are doing globally to resolve the issue.
For instance, the US has given a deadline to change all the older altimeters by May 31 this year and the replacement of the altimeters is currently on.
Brazil and some central American countries have also given a timeline within which the old altimeters have to be replaced.
Indian telcos are urging the government to put in place a clear deadline on this, so that aircraft companies can execute the replacement.
At present the replacements are being undertaken on a first-come-first-served basis.
The aircraft companies have said they can determine the maximum permissible radiation from a tower with 5G radios that would not interfere with the older altimeters.
For this, telcos have to provide them with the details of their 5G antennae, so that it is possible for them to determine the power.
A senior executive of a telco said: "If the airlines are not given a clear deadline to change the altimeters by the DGCA, why should they do it voluntarily? It means that the aircraft will be grounded for a while and lose money."
The ministry of civil aviation had asked telecom companies last year to create a buffer and safety zone to ensure mitigation measures while implementing C-band 5G spectrum in and around an airport.
It has told telcos that there should not be any base station for the 3.3 GHz-3.67 GHz frequency range in the 2,100 metres from both ends of the runway and 910 metres from the central line of the runway.
Also, base stations beyond this zone, in a radius of 540 metres, can operate only at lower powers limited to 58 dBm of the same band, and telcos should ensure downward tilting of these 5G base stations to the extent that 5G signals do not interfere with radio altimeters.
The move, according to telcos, would essentially mean that they would not be able to give 5G services on the crucial band in and around airports and in nearby residential and commercial areas.
They point out that given the high cost of the spectrum they have paid for, the department of telecommunication should compensate them if they are not able to put it to commercial use at airports and nearby areas.
The directive by the DGCA comes amid global concerns that the 5G band could interfere with aircraft radio altimeters, especially when many aircraft are of old vintage.
Radio altimeters measure altitude above the terrain to determine the path of the aircraft, along with GPS.
They also help them gauge highrises, mountains, and other obstacles in low visibility.
But telcos argue that the band used by altimeters is 4.2 GHz, and not 3.3-3.67 GHz, which has been auctioned for 5G services in the country.
So there is a gap of 500 MHz and, hence, there is no real chance of any interference, they said.
Telcos said they had requested the DGCA to test if there was any interference as was done in some European countries, but the request was denied.