Story ID: 460
Dynamic Curtailment Added to APG iPreFlight App
By: Matt Thurber
Caption: The new feature enables operators to account for changes in center of gravity during flight.
Word Count: 563

Aircraft Performance Group (APG, Booth 3170) has released a major update to its iOS-based runway analysis app’s weight-and-balance function, a real-time curtailment feature that accounts for changes in loading during flight to help operators ensure the aircraft remains within CG limitations from takeoff to touchdown.

The new dynamic curtailment feature in APG’s iPreFlight app meets the recommendations of AC 120-27E, the FAA’s advisory circular on weight-and-balance control. The benefit of considering curtailment effects is that accounting for in-flight changes in fuel load, passenger movement, consumption of fluids, etc., can allow the operator to extract more performance, as opposed to applying a fixed curtailment, worst-case-scenario loading situation. “That can be a problem if the load pushes the CG out of that fixed part of the weight-and-balance envelope,” said APG CEO Mike Caflisch. “The dynamic curtailment feature is based on the actual load, so you don’t overly curtail when you don’t need to, which could lead to lower payload or operational restrictions. This is something that is not fairly well understood,” he added. “We’ve been getting more calls from operators getting called on it by FAA POIs [principal operations inspectors] wondering how they comply.”

Business Aviation Application

Airlines have been using dynamic curtailment for years, but in a zonal fashion, which works well because they are flying larger airplanes, and dynamic curtailment can be handled within each zone. The Embraer Lineage 1000, for example, is set up in a zonal scheme on iPreFlight, but other jets use the specific location of seats and equipment, which APG programs into each customer’s aircraft files. “It’s an APG-engineering curtailment,” he explained. “It’s a pretty substantial documentation requirement, a substantiation report that we provide back to the operator that shows exactly the arm and moment of every item that has to be considered. It reflects how the CG changes when, say, the pilot moves aft to the lavatory or the flight attendant pushes a galley cart aft.”

As part of iPreFlight, the dynamic curtailment calculations are “tightly incorporated into our runway performance analysis,” Caflisch said. Dynamic curtailment is a premium feature, so there is an extra fee for iPreFlight subscribers.

APG has also developed another new iPreFlight feature, a separate cold-weather operations app for determining adjustments to altitudes during instrument approach procedures when temperatures are colder than normal. The user will be able to enter an airport ID and the temperature and quickly see the necessary adjustments without having to run the numbers in the FMS or calculate the restrictions separately. The app will work offline, too.

Here at the NBAA show, APG is holding workshops to teach pilots how to use iPreFlight and its core runway analysis features. The sessions begin with an explanation of takeoff performance regulations and standards and then how runway analysis is used to maximize payload, including the best way to switch to an APG-derived procedure after an engine fails during takeoff. Sessions are scheduled November 1 and 3 at 1 p.m., and November 2 at 10 a.m.

“There is a growing understanding of runway analysis,” said Caflisch. “We’ve spent a lot of years educating pilots and trying to explain the regulations. It doesn’t matter whether you’re a 91, 121, 135 or 125 operator, here is a great tool that’s easy to use.”