Here is the whole thing.
In radar environment it says 7 minutes.
I was getting ahead of myself by trying to come up with a scenario, where in some remote location (Diversion,etc) I might lose radar contact shortly after Takeoff, and have radio failure.
Like I said not likely at all, but thanks for all the replies.
ICAO RADIO FAILURE PROCEDURES
Visual Meteorological Conditions: Same as domestic operations.
Instrument Meteorological Conditions - Nonradar Environment
If failure occurs in IMC and the guidance for VMC cannot be complied with, continue the flight as follows. See the Regions chapter for any regional navigation procedures that may apply.
• Maintain the last assigned speed and flight level, or minimum flight altitude, if higher, for a period of 60 minutes following a failed position report over a compulsory reporting point.
• After 60 minutes, adjust flight level and speed in accordance with the filed flight plan.
Instrument Meteorological Conditions - Radar Environment
If failure occurs in IMC and the guidance for VMC cannot be complied with, continue the flight as follows. See the Regions chapter for any regional navigation procedures that may apply.
• Maintain the last assigned airspeed and flight level, or minimum flight level, if higher, for a period of 7 minutes following the:
- Time the last assigned flight level or minimum flight altitude is reached, or
- Time the transponder is set to code 7600, or
- Airplane’s failure to report its position over a compulsory reporting point, whichever is later.
• Thereafter, adjust flight level and speed in accordance with the filed flight plan.
- When being radar vectored or having been directed by ATC to do a route offset without a specified limit, proceed in the most direct manner possible to rejoin the current flight plan route no later than the next significant point, taking into consideration the applicable minimum flight altitude.
- Proceed according to the current flight plan route to the appropriate designated
navigation aid or fix serving the destination airport and hold, if required, until
commencement of descent.
- Commence descent from the navigation aid or fix serving the destination airport as
close as possible to the expected approach time last received and acknowledged. If
there was no expected approach time received and acknowledged, commence
descent as close as possible to the estimated time of arrival from the current flight plan.
- Complete a normal instrument approach procedure as specified for the designated navigation aid or fix and land.