Descend to 5000' is the correct Australian phrase.
DeBurcs comment is correct. The misinterpretation of the use of “two” as “to” in the descent clearance was the probable cause of the loss of the Flying Tiger B747 freighter at Kuala Lumpur.
As a result to avoid confusion ATC agencies worldwide adopted changes to preclude the use of the word to in altitude clearances (which parodoxically was what the KUL controller used). Oz took the opposite tact for probably for much the same reasons.
In non-English speaking countries odd bits of speech such as to are commonly left out. So the International default eliminated it also.
Perhaps we will need another “Flying Tiger” before we can agree on joining the rest of the ICAO World in standardizing ATC procedures based on the experience of others.
OVC002
Date: 19 FEB 1989
Time: 06:36
Type: Boeing 747-249F
Operator: Flying Tiger Line
Registration: N807FT
Msn / C/n: 21828/408
Year built: 1979
Total airframe hrs: 34000 hours
Cycles: 9000 cycles
Engines: 4 Pratt & Whitney JT9D-7Q
Crew: 4 fatalities / 4 on board
Passengers: 0 fatalities / 0 on board
Total: 4 fatalities / 4 on board
Airplane damage: Written off
Location: 12 km (7.5 mls) from Kuala Lumpur (Malaysia)
Phase: Approach (APR)
Nature: Cargo
Departure airport: Singapore
Destination airport: Kuala Lumpur-Subang Airport (KUL)
Flightnumber: 66
Narrative:
The Boeing, named "Thomas Haywood", was less than half loaded with textiles, computer software and mail when it departed Singapore. Approaching Kuala Lumpur, the crew were cleared to route direct to the Kayell (KL) beacon for a runway 33 approach. While on the NDB approach, the crew were cleared to "...descend two four zero zero..." which was interpreted by the crew as "...to 400...". The aircraft descended below minimum altitude and crashed into a hillside at 600 feet/180m msl just before reaching the Kayell NDB, where minimum descent height was 2400 feet. The Boeing hit treetops and started to break up until bursting into flames.
PROBABLE CAUSE: Non-standard phraseology was used by Kuala Lumpur ATC, causing the crew to misinterpret the instructions.