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AIM

10/12/17

5−3−24

En Route Procedures

6. Use of RNAV Distance in lieu of DME

Distance. Substitution of RNAV computed distance

to or from a NAVAID in place of DME distance is

permitted when holding. However, the actual holding

location and pattern flown will be further from the

NAVAID than designed due to the lack of slant range

in the position solution (see FIG 5−3−7). This may

result in a slight difference between RNAV distance

readout in reference to the NAVAID and the DME

readout, especially at higher altitudes. When used

solely for DME substitution, the difference between

RNAV distance to/from a fix and DME slant range

distance can be considered negligible and no pilot

action is required.

REFERENCE−

AIM Paragraph 1−2−3, Use of Suitable Area Navigation (RNAV) Systems

on Conventional Procedures and Routes

FIG 5−3−7

Difference Between DME Distance From NAVAID & RNAV Computed Distance From NAVAID

7. Use of RNAV Guidance and Holding.

RNAV systems, including multi−sensor Flight

Management Systems (FMS) and stand−alone GPS

receivers, may be used to furnish lateral guidance

when executing a hold. The manner in which holding

is implemented in an RNAV system varies widely

between aircraft and RNAV system manufacturers.

Holding pattern data may be extracted from the

RNAV database for published holds or may be

manually entered for ad−hoc ATC−assigned holds.

Pilots are expected to be familiar with the capabilities

and limitations of the specific RNAV system used for

holding.

(a) All holding, including holding defined on

an RNAV or RNP procedure, is based on the

conventional NAVAID holding design criteria,

including the holding protected airspace construc-

tion. There are differences between the holding entry

and flight track assumed in conventional holding

pattern design and the entry and track that may be

flown when RNAV guidance is used to execute

holding. Individually, these differences may not

affect the ability of the aircraft to remain within

holding pattern protected airspace. However, cumu-

latively, they can result in deviations sufficient to

result in excursions up to limits of the holding pattern

protected airspace, and in some circumstances

beyond protected airspace. The following difference

and considerations apply when an RNAV system

furnishes the lateral guidance used to fly a holding

pattern:

(1) Many systems use ground track angle

instead of heading to select the entry method. While

the holding pattern design allows a 5 degree

tolerance, this may result in an unexpected entry

when the winds induce a large drift angle.

(2) The holding protected airspace is based

on the assumption that the aircraft will fly−over the

holding fix upon initial entry. RNAV systems may

execute a “fly−by” turn when approaching the

holding fix prior to entry. A “fly−by” turn during a

direct entry from the holding pattern side of holding

course may result in excursions beyond protected

airspace, especially as the intercept angle and ground

speed increase.

(3) During holding, RNAV systems furnish

lateral steering guidance using either a constant bank

or constant radius to achieve the desired inbound and

3/15/07

7110.65R CHG 2

AIM

9/13/18