NPRM streamlines rules for Part 23 certification

 - September 30, 2009, 6:02 AM

The FAA has issued a notice of proposed rulemaking (NPRM) that will attempt to close some loopholes in the Part 23 regulations under which light jets and other airplanes are certified. The NPRM is open for comments until November 16, and the easiest way to view the proposal is to search the term “Docket No. FAA–2009–0738” at

Until the Cessna Citation 501 series came to market in the 1970s, most jets were certified to Part 25 transport-category regulations, in-cluding the first Cessna Citation. One notable exception was the Lear 23, although subsequent Learjets were certified under Part 25. Because Part 23 didn’t address jet aircraft requirements, the FAA has had to add a large number of special conditions each time a jet is certified under Part 23. The NPRM would fold many of the items that led to repeated special conditions into the new rules.

Some of the issues that the new rules would address include making sure Part 23 jets have a minimum one-engine-inoperative performance level equivalent to Part 25 requirements; sensitivity of turbine engines to altitude and temperature effects; and high takeoff and landing speeds associated with jets compared to typical Part 23 multiengine piston-powered airplanes. All of the proposed changes stem from aviation rulemaking committee recommendations.

One area that is subject to change under the proposed rules is the one-engine inoperative (OEI) climb gradient, which special conditions had pegged at 2 percent for multiengine jets with an mtow of greater than 6,000 pounds. The new rules would codify that requirement and impose a 1.2-percent gradient on airplanes with an mtow of less than 6,000 pounds. Thus far only one VLJ meets that criterion, the Eclipse 500.

The FAA believes that the lower gradient is acceptable because “we wanted to compromise by proposing a requirement that would provide an adequate minimum safety standard and encourage production of more jets. One multi- engine jet [the Eclipse 500] in this weight band has been operated as an air taxi, and the FAA expects this type of operation to grow. While this particular jet is capable of higher climb performance, we propose only to increase the OEI climb performance requirement to 1.2 percent because other jets in this weight band may not be capable of the higher 2-percent climb performance. Based on accident data, 1.2 percent provides an adequate minimum safety standard.”

The current rules require only that a sub-6,000-pound jet demonstrate a “measurably positive” climb gradient with one engine inoperative. The proposed rules would also apply a specific percentage to other aircraft types: 1 percent for pistons weighing more than 6,000 pounds and all Part 23 turboprops.

Other proposed changes address a host of issues, including landing reference speeds, flight characteristics, takeoff warning systems, crashworthiness (dynamic seat testing and head-injury criteria), high-altitude structural integrity, fuselage-embedded engine fire safety and advanced avionics and integrated electronics systems.