Penetration From Holding
Depending on the goal, choose an appropriate method to accelerate from holding airspeed to 250 KIAS
(TACAN penetration airspeed).
1. For fuel conservation, plan to intercept 250 KIAS as you descend out of altitude. At the fix, lower the
nose and begin descent while accelerating to 250 KIAS. As airspeed approaches 250 KIAS, reduce
power to IDLE and extend the speed brakes if necessary.
2. For timing considerations (for example, CV approaches), accelerate to arrive at the IAF at 250 KIAS.
Once cleared inbound and on course, perform a level speed change from 200 KIAS to 250 KIAS.
At the IAF, simultaneously lower the nose and accelerate to 250 KIAS. At 250 KIAS, reduce power to
IDLE and adjust nose attitude and trim to maintain speed, countering the resulting nose pitchup with
forward stick. Retrim for 250 KIAS. Descending at idle, 250 KIAS with speed brakes extended yields
approximately 4,000 fpm or 1,000 ft of altitude loss for each nautical mile (no wind). Idle, 250-kt clean
descent yields approximately 2,000 fpm or 1,000 ft of altitude loss for every two nautical miles.
NOTE: To begin penetration, the aircraft must be established on initial approach course.
During approaches to airfields, retract boards when the profile allows and maintain 250 KIAS. Unlike
airfield approaches, CV penetrations are closely sequenced and require all aircraft to maintain 250 KIAS
and 4,000 fpm until 5,000 ft AGL, also known as platform. At platform, CV aircraft reduce the rate of
descent from 4,000-2,000 fpm by retracting speed brakes and maintaining 250 KIAS. The T-45C
NATOPS, Chapter 8, provides more details concerning carrier approaches.
During field approaches, call, Platform, and retract the speed brakes if practical. Regardless, honor the
Enroute descents are used to transition from an enroute altitude to the final portion of an instrument
approach or visual approach in lieu of published penetrations. An enroute descent can also be flown to a
GCA pickup. The routing on this descent may be via radar vectors or the NAVAIDs depicted on the high
You may request, or a controller may initiate, an enroute descent; however, the controller must advise you
of his or her intention to provide this service, and you may refuse it in favor of a published instrument
approach. Prior to issuing descent clearance below the highest published IAF for an airport, the controller
must advise you of the type of approach to expect, current altimeter setting, and the current weather, if the
ceiling is below 1,000 ft AGL or the highest published circling minimums (whichever is greater), or if
visibility is less than 3 miles.
ENROUTE DESCENT PLANNING
Goal: Reduce time to destination by descending at an IAS that is higher than the max range airspeed.
This type of descent is used when saving fuel is less important than time-to-destination.
Procedure: To calculate VSI, divide altitude to lose by nm-to-go times groundspeed. For example,
cruising at FL300 and center clears you to descend and maintain 15,000 ft in the next 50 miles.
Substituting these numbers into our equation: (-15,000 ft/50 nm) (5 nm/min) equals -1,500 ft per min. Of
course, the specific VSI depends on groundspeed, but the following table provides a rough approximation.