approach altitude of 5,000 feet to be selected in the altitude  pre-selector window. This step is very important because  accurate FD guidance is not available to the PF during a  missed approach if the MDA is left in the window.  Note: See“Maximum Acceptable Descent Rates”under the  heading “Descent Rates and Glide paths for Non-precision  Approaches. ”  In IMC, you must continuously evaluate instrument  information throughout an approach to properly maneuver  the aircraft or monitor autopilot performance and to decide  on the proper course of action at the decision point (DA,  DH, or MAP). Significant speed and configuration changes  during an approach can seriously degrade situational  awareness and complicate the decision of the proper action  to take at the decision point. The swept wing handling  characteristics at low airspeeds and slow engine response  of many turbojets further complicate pilot tasks during  approach and landing operations. You must begin to form  a decision concerning the probable success of an approach  before reaching the decision point. Your decision-making  process requires you to be able to determine displacements  from the course or glideslope/glidepath centerline, to  mentally project the aircraft’s three-dimensional flight path  by referring to flight instruments, and then apply control  inputs as necessary to achieve and maintain the desired  approach path. This process is simplified by maintaining a  constant approach speed, descent rate, vertical flight path,  and configuration during the final stages of an approach.  This is referred to as the stabilized approach concept.  Operational experience and research have shown that a  descent rate of greater than approximately 1,000 fpm is  unacceptable during the final stages of an approach (below  1,000 feet AGL). This is due to a human perceptual limitation  that is independent of the type of airplane or helicopter.  Therefore, the operational practices and techniques must  ensure that descent rates greater than 1,000 fpm are not  permitted in either the instrument or visual portions of an  approach and landing operation.  For short runways, arriving at the MDA at the MAP when  the MAP is located at the threshold may require a missed  approach for some aircraft. For non-precision approaches,  a descent rate should be used that ensures the aircraft  reaches the MDA at a distance from the threshold that  allows landing in the TDZ. On many IAPs, this distance is  annotated by a VDP. If no VDP is annotated, calculate a  normal descent point to the TDZ. To determine the required  rate of descent, subtract the TDZE from the FAF altitude  and divide this by the time inbound. For example, if the  FAF altitude is 2,000 feet MSL, the TDZE is 400 feet MSL  and the time inbound is two minutes, an 800 fpm rate of  descent should be used.  A stabilized approach is essential for safe turbojet operations  and commercial turbojet operators must establish and  use procedures that result in stabilized approaches. A  stabilized approach is also strongly recommended for  propeller-driven airplanes and helicopters. You should limit  configuration changes at low altitudes to those changes  that can be easily accommodated without adversely  affecting your workload. For turbojets, the aircraft must  be in an approved configuration for landing or circling,  if appropriate, with the engines spooled up, and on the  correct speed and flight path with a descent rate of less  than 1,000 fpm before descending below the following  minimum stabilized approach heights:  To verify the aircraft is on an approximate three degree  glidepath, use a calculation of 300 feet to 1 NM. The  glidepath height above TDZE is calculated by multiplying  the NM distance from the threshold by 300. For example,  at 10 NM the aircraft should be 3,000 feet above the TDZE,  at 5 NM the aircraft should be 1,500 feet above the TDZE,  at 2 NM the aircraft should be 600 feet above the TDZE, and  at 1.5 NM the aircraft should be 450 feet above the TDZE  until a safe landing can be made. Using the example in the  previous text, the aircraft should arrive at the MDA (800  4-37 • For all straight-in instrument approaches, to include  contact approaches in IFR weather conditions, the approach must be stabilized before descending below 1,000 feet above the airport or TDZE. • For visual approaches and straight-in instrument approaches in VFR weather conditions, the approach  must be stabilized before descending below 500 feet  above the airport elevation. • For the final segment of a circling approach maneuver, the approach must be stabilized 500 feet  above the airport elevation or at the MDA, whichever  is lower. These conditions must be maintained throughout the approach until touchdown for the approach to be considered a stabilized approach. This also helps you to recognize a wind shear situation should abnormal indications exist during the approach. Descents  Stabilized Approach  Descent Rates and Glidepaths for Nonprecision  Approaches  Maximum Acceptable Descent Rates 