Originally Posted by Someone83

Don't now the details of it, but there are quite strict restrictions regarding APU use at gate in CPH

Originally Posted by CPH Env Report 2008

The noise impact from aircraft on the ground primarily
comes from engine run-ups, but the use of APUs also
contributes to the noise exposure. Most jet aircraft have
an APU, a small jet engine which produces power and
pressurised air for the aircraft when it is on the ground
and the main engines are turned off. To reduce noise, the
APU may only be used for five minutes before the aircraft
leaves the stand and five minutes after it arrives at the
stand. For the rest of the time, the aircraft must use the
power and ventilation facilities provided by the airport at
most stands. At 103 out of the 121 numbered stands at
Copenhagen Airport, we have installed stationary power
supply facilities for aircraft. At stands that do not have
these facilities, the aircraft can use a GPU (ground power
unit), which is a diesel or electrically powered generator
that emits considerably less noise than an APU. CPH made
regular inspections during the year to monitor the use of
APUs at the aircraft stands.
In 2008, 117 inspections were made to check the use of
APUs by aircraft; a representative selection of the airport’s
stands used for jet aircraft were inspected. In 75 cases, the
rules were complied with, whilst the conditions for use of
APUs were not complied with in 42 cases. Accordingly,
36% of the inspections showed violation of the rules. An
evaluation of the last four years of aircraft stand inspections
shows that stands with power and ventilation facilities
showed a decline in violations from 62% in 2005 to
13% in 2008. The stands that do not have these facilities
saw only a small drop in violations, in spite of a campaign
to observe the rules in force brought about by the fact
that in 2008 every second aircraft (52%) did not comply
with the rules. The campaign will continue at a greater
intensity in 2009.
In connection with most of the recorded violations, CPH
took direct action by boarding the aircraft in question and
notifying the pilot that the airport’s rules on use of APUs
must be complied with.