Impact of Relocated Threshold
Runway Safety Area of 300 Feet and
Analysis of March 7, 2008 Runway Safety
Area Proposal Submitted by the FAA
March 20, 2008
At the request of Congressman Waxman, the City of
The installation of 300 foot RSA’s at both ends of the
runway would result in a reduction of runway length from the current 4973 feet
to 4500 feet available for takeoff or landing in either direction. The 300 foot RSA’s would meet the FAA’s RSA standard
for category A & B aircraft – the preponderance of the aircraft using the
Airport and for which the facility was designed to safely accommodate. It would not however meet the RSA standard for
the more demanding category C and D aircraft which require a 1,000 foot flat
surface RSA or an equivalent EMAS bed to meet FAA standards. That equivalency is an EMAS bed that can stop
a category C or D aircraft leaving the end of the runway at 70 knots or less. However, by incorporating an appropriately
sized EMAS bed within the 300 foot RSA, this safety option would move closer to
meeting federal RSA standards for all aircraft currently utilizing the
Of the 127,036 total aircraft operations at
The remaining 8,510 jet aircraft operations, or 6.7% of
total aircraft operations at
It is also unlikely that reducing the available runway to 4,500
feet would have any impact on passenger load, as a survey by the staff of the
Many aircraft that would potentially be affected by a 4,500
foot runway are already affected by the current
runway length of 4,973 feet at SMO. These more demanding category C and D
business jets are currently operating at the edges of safety without the
protection of any federally mandated runway safety areas. Reducing
the effective runway length from 4,973 feet to 4,500 feet to accommodate 300
foot RSAs could further limit, for instance, the amount of fuel that these
aircraft could carry at takeoff, but would not prohibit their operation at the
For landings, the potential impacts are related to the Federal
Air Regulations (FARs) under which the specific aircraft operations are being conducted. Jet operations at SMO are conducted under one
of three sets of FARs. Privately owned
and/or operated aircraft are subject to FAR Part 25. Aircraft operating for hire (air taxi) must
comply with FAR Part 135. This affects
the calculated landing length as the pilot must determine if the aircraft can
land within 60 percent of the available runway length. Fractional share aircraft are required to
operate under FAR Part 91(subpart k).
These aircraft must also operate within the 60 percent rule unless the
operation is conducted in accordance with an approved “Destination Airport
Analysis”. With this approved analysis,
the fractional aircraft is allowed to operate within 80 percent of the
available runway length. It can be
assumed that most of the fractional operators desiring to operate at
Finally, consideration must be given to the fact that participants in fractional aircraft ownership arrangements, or those individuals who charter aircraft, are readily able to switch to other aircraft that would not be affected by limitations related to runway length. Thus, if someone did not want to comply with the necessary operational limits on their first choice of aircraft, could, in many cases, readily switch to another aircraft that can safely operate out of a 4,500 foot runway with even less significant restrictions.
Assumptions
Runway length requirements vary between aircraft type which are also affected by myriad other operating conditions and variables. For all aircraft operations (including business jets), the runway length required for a given flight/stage length considers: the airport’s elevation, temperature, atmospheric pressure, wind direction and velocity, available runway length and gradient (slope), runway surface condition (wet/dry), the aircraft’s performance characteristics and the respective useful load factor and payload anticipated for a given flight.
The airport elevation and runway gradient are set for a
given runway. At
For purposes of analysis Coffman based performance
characteristics of the aircraft using an assumed yearly average temperature for
Additionally, based on the fact that Santa Monica Airport averages
very few days of rain, we have assumed a dry pavement. Wet pavement can affect
the friction coefficient of a runway and therefore, length calculations
typically include an additional safety factor for operating from a wet runway,
particularly on landing.
The gradient has the greatest impact on Runway 3 (east flow) takeoff requirements. Departing to the east, the upward gradient of the runway requires more effort to reach the critical speed for takeoff. The downhill slope on Runway 21 assists the aircraft in accelerating to the critical takeoff speed earlier. Thus, less runway length is necessary for departures to the west. Approximately 95 percent of all operations are on Runway 21. For purposes of this analysis, the runway length at maximum takeoff weight as well as at 60% useful load was calculated with a gradient correction for Runway 3.
Since takeoffs on Runway 21 require less runway length, a separate takeoff length at 60 percent useful load was also calculated. While the downhill slope in this direction would serve to reduce the runway length required, no gradient correction was used. This conservatively overestimates the runway length requirement for Runway 21.
The maximum useful load of an aircraft is considered to be the difference between the maximum allowable gross weight and the operating empty weight. In essence, the useful load consists of passengers, cargo, and usable fuel. At SMO, which has no cargo operations and averages just under two passengers and rarely more than four passengers per flight, the useful load primarily relates to the amount of fuel carried. As a benchmark to show the affect of a 4,500 foot runway, we have assumed a useful load of 60 percent for takeoff. This is based upon the runway length that FAA is typically willing to fund at general aviation airports. Reducing the useful load below 60 percent simply reduces the amount of fuel that may be carried and, therefore, the distance that the aircraft can fly nonstop. When aircraft fly short distances, as typically is the case from SMO, there may be no impact at all on such operations.
Table A - Takeoff
Length Analysis presents the runway takeoff length requirements for
aircraft operating into
Under the stated conditions, all of the evaluated aircraft using the Airport were able to safely takeoff at a 60 percent load factor within 4,500 feet on Runway 21. All of the evaluated aircraft, except for 8 aircraft types representing only 1212 takeoffs in total, could takeoff from Runway 3 under the same conditions. Since Runway 3 is only used approximately 5% of the time, only 61 annual takeoffs would be affected during Runway 3 operations (5% of the 1212 takeoffs mentioned above).
Table B - Landing Length Analysis presents the
runway length requirements for landing under FAR Part 25, Part 91(K) , and Part
135 regulations. All aircraft could land
under Part 25 regulations and the stated conditions. Analysis of Part 91(K) operations using
maximum certificated gross landing weights indicate that a vast majority of the
Part 91(K) operations can safety use a 4,500 foot runway. As shown on Table B, a minor reduction in gross
landing weight would permit the small number of aircraft affected by a 4,500
foot runway to continue operating under Part 91(K) at the
Assuming that the major fractional operators have had
FAA PROPOSAL
The FAA’s most recent proposal transmitted to the City on March 7, 2008, contains two options: (1) EMAS beds of 130 feet with a 25 foot lead-in at both ends of the runway; or (2) a 250 foot EMAS bed with a 25 foot lead in at the west end of the runway with no runway safety option on the east end of the runway. Both proposals are non-standard runway safety area options that do not meet the FAA’s standard for stopping an aircraft departing the end of the runway at a speed of 70 knots or less. The first option of 130 foot EMAS beds is only intended to stop an aircraft departing the end of the runway at a speed of 40 knots or less. Although the second option has been characterized as a 70 knot standard proposal, modeling by ESCO, the manufacturer of EMAS indicates that the proposed 250 foot EMAS bed and 25 foot lead-in would not meet the 70 knot standard for 5 of the 7 aircraft modeled for the FAA by ESCO.
EMAS is currently not effective for aircraft weighing 12,500 pounds of less. For the safety design analysis for lighter aircraft, the EMAS bed must be treated as if it were a regular surface beyond the end of the runway. Since these lighter aircraft make up over 85 percent of the Airport’s operations, it is important that the 300 foot RSA design standard for these lighter aircraft be met. As an airport that has planned, designed and maintained its facilities pursuant to the B-II standards agreed to in the Santa Monica Airport Agreement (“1984 Agreement”) between the FAA and the City of Santa Monica, the Airport needs runway safety areas that meet the FAA’s standards for a B-II airport. Given the increase in stopping power of EMAS with incremental increases in size, it appears that safety options that meet the 70 knot standard, but also preserve the utility of the Airport’s runway, are feasible with a minimal impact on aircraft users.
CONCLUSION
Our extensive operational analysis indicates that the
utility of the
Prepared by: Coffman Associates
Kaplan, Kirsch & Rockwell
City Staff
Attached Take Off and Landing Analyses Prepared by: Coffman Associates
3/21/08