functionally two portions to the EGI, an inertial navigation unit (INU) and the global positioning receiver.
When aligning the EGIs with a new position coordinate, it is important that the entering of the new
position take place in the initial alignment sequence of the EGIs while the "HDG" selection is displayed on
the TSD page. In doing so, this helps to insure a good alignment of the ring laser gyros takes place.
Entering of the position coordinate, correct Zulu time and date resets the global positioning receiver and
allows it to find the proper satellite constellation. It is possible to have a very large position error (in the
case of the incident aircraft over 600 nautical miles) and still have a normal display of GPS information on
the TSD utility page. In this case, the EGIs would disregard the GPS input because of the large position
d. The AH--64D has sufficient control power to overcome an uncommanded scheduling of the
stabilator within normal operating conditions. The stabilator is electrically powered and takes
approximately 6 seconds to schedule from a trailing--edge--up position to full trailing--edge--down.
Depending on airspeed, this event can generate significant aircraft pitch changes and decelerative forces.
The instinctive AFT cyclic input applied will begin to slow the aircraft. However, a reduction in collective
generates an additional pitch down moment and decreases the amount of thrust the main rotor can
produce, aggravating this situation. The crew should react normally to the emergency, moderating power
and cyclic inputs to slow the aircraft and avoid obstacles. Aircraft control is the first and overriding
consideration. Rapid aircraft pitch changes may also cause a momentary flickering of the ACC oil PSI
caution message with tone. If the stabilator is slewed down in response to an erroneous velocity
generated by the EGI, that velocity would be displayed on the MPDS and HDU. As such, the same
erroneous velocity that caused the stabilator to slew down, also allows the pilot to take manual control of
the stabilator and return it to an appropriate position.
e. The following is provided with regard to procedures for the AH--64D Longbow Apache --
Unit commanders will provide an initial briefing on the contents of this TB
to assigned AH--64D aviators prior to their next flight.
Unit commanders will place a copy of this TB in the units aircrew reading
(1) Urgent change to TM 1--1520--251--10, page 8--9, para 8.16A and 8.16B, add --
(a) 8.16A *EGI Operational Check Pilot/CPG.
1. TSD and flight page -- select.
2. Heading, attitude, and position verify.
3. TSD utility page -- select. Note position confidence value, verify current date and time.
4. Secondary EGI -- select as primary. Note position confidence value, verify current
date and time.
5. TSD page -- select.
6. PP button -- select. Verify position.
7. TSD utility page -- Select EGI with lowest position confidence value as primary.