background image

6/17/21 

AIM 

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

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 

En Route Procedures 

5

3

25