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Figure 7-2. V MINI Limitations, Maximum IFR Approach Angles and G/A Mode Speeds for selected IFR-certified helicopters.
7-3
7-4
feet per NM. At 70 KIAS (no wind) this equates to a
descent rate of 925 FPM. With a 10-knot tailwind the
descent rate increases to 1,056 FPM. “Copter” PinS
approach procedures are restricted to helicopters with a
maximum V MINI of 70 KIAS and an IFR approach angle
that will enable them to meet the final approach
angle/descent gradient. Pilots of helicopters with a V MINI
of 70 KIAS may have inadequate control margins to fly
an approach that is designed with the maximum allowable angle/descent gradient or minimum allowable
deceleration distance from the MAP to the heliport. The
“Copter” PinS final approach segment is limited to 70
KIAS since turn containment and the deceleration distance from the MAP to the heliport may not be adequate
at faster speeds. For some helicopters, (highlighted yellow in Figure 7-2) engaging the autopilot may increase
the V MINI to a speed greater than 70 KIAS, or in the “goaround” mode require a speed faster than 70 KIAS. It
may be possible for these helicopters to be flown manually on the approach, or on the missed approach in a
mode other than the G/A mode.
Since slower IFR approach speeds enable the helicopter to
fly steeper approaches and reduces the distance from the
heliport that is required to decelerate the helicopter, you
may want to operate your helicopter at speeds slower than
its established V MINI . The provision to apply for a determination of equivalent safety for instrument flight below
V MINI and the minimum helicopter requirements are specified in Advisory Circulars (AC) 27-1, Certification of
Normal Category Rotorcraft and AC 29-2C, Certification
of Transport Category Rotorcraft. Application guidance is
available from the Rotorcraft Directorate Standards Staff,
ASW-110, 2601 Meacham Blvd. Fort Worth, Texas
76137-4298, (817) 222-5111.
Performance data may not be available in the
Helicopter Flight Manual for speeds other than the
best rate of climb speed. To meet missed approach
climb gradients pilots may use observed performance
for similar weight, altitude, temperature, and speed conditions to determine equivalent performance.
When missed approaches utilizing a
climbing turn are flown with an
autopilot, set the heading bug on the
missed approach heading, and then
at the MAP, engage the indicated
airspeed mode, followed immediately by applying climb power and
selecting the heading mode. This is
important since the autopilot roll
rate and maximum bank angle in
the Heading Select mode are significantly more robust than in the NAV
mode. Figure 7-3 represents the
bank angle and roll limits of the S76 used by the FAA for flight test-
ing. It has a roll rate in the Heading Select mode of 5
degrees per second with only 1 degree per second in
the NAV mode. The bank angle in the Heading Select
mode is 20 degrees with only 17 degrees in the NAV
Change Over mode. Furthermore, if the Airspeed
Hold mode is not selected on some autopilots when
commencing the missed approach, the helicopter
will accelerate in level flight until the best rate of
climb is attained, and only then will a climb begin.
Wide area augmentation system (WAAS) localizer performance (LP) lateral-only PinS testing conducted in
2005 by the FAA at the William J. Hughes Technical
Center in New Jersey for helicopter PinS also captured
the flight tracks for turning missed approaches. [Figure
7-4] The large flight tracks that resulted during the
turning missed approach were attributed in part to operating the autopilot in the NAV mode and exceeding the
70 KIAS limit.
OPERATIONS SPECIFICATIONS
A flight operated under Part 135 has minimums and
procedures more restrictive than a flight operated under
Part 91. These Part 135 requirements are detailed in
their operations specifications (OpsSpecs). Helicopter
Emergency Medical Service (HEMS) operators have
even more restrictive OpsSpecs. Figure 7-5 on page
7-6 is an excerpt from an OpsSpecs detailing the minimums for precision approaches. The inlay in Figure
7-5 shows the minimums for the ILS Rwy 3R
approach at Detroit Metro Airport. With all lighting
operative, the minimums for helicopter Part 91 operations are a 200-foot ceiling, and 1200-feet runway
visual range (RVR) (one-half airplane Category A
visibility but no less than 1/4 SM/1200 RVR).
However, as shown in the OpsSpecs, the minimum
visibility this Part 135 operator must adhere to is
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Instrument Procedures Handbook (IPH)仪表程序手册下(152)
