Cessna Citation II 1200 Pound Gross Weight Increase
How were you able to accomplish this takeoff weight increase? Aircraft designs are always compromises. To achieve certain objectives, many different factors must be considered. To increase the gross weight of an aircraft, one could add structure (which adds weight), reduce zero fuel weight (zero fuel weight is the primary factor that determines how much structural strength is required), or limit airspeed. Cessna chose to add structure when they incorporated an 800 pound increase at 550-0627 on new aircraft. New Flight decided a structural beef-up on an existing airframe would be prohibitively expensive. We therefore chose two other possible solutions: (1) reduce the maximum speed of the aircraft, or (2) reduce the zero fuel weight.
Configuration Changes
Which solution did New Flight choose?
We actually have two configurations of the STC. That means you can choose which way you would like to go.
Configuration 1 reduces the maximum operating speed (Vmo) to 227 knots compared with 262 knots for the unmodified aircraft. This speed limitation was necessary to allow the increase in takeoff weight without structural beef-up.
Configuration 2 reduces the maximum zero fuel weight to 10,000 lbs. (for takeoff weights above 14,100) compared to 11,000 lbs. for the unmodified aircraft. It should be pointed out that the original maximum zero fuel weights of 11,000 lbs. may still be used if the takeoff weight is limited to 14J00 lbs. Once again, this limitation was necessary to allow the increase in takeoff weight without structural beef-up. Either condition will work. You choose the best configuration for your own set of conditions. To date the customers have always chosen the zero fuel weight reduction configuration.
What are the consequences of reducing maximum Zero Fuel Weight from 11,000 lbs. to 10,000 lbs.?
None, really. Since the average Basic Operation Weight (BOW) is around 8400 lbs., this leaves 1600 lbs. available for passengers and baggage. For those operators with higher BOW's our STC offers the ability to takeoff at weights slightly lower than 14,500 lbs. but at higher zero fuel weights. Specifically:
Max. ZFW
10,000
10,500
10,950
Max. T.O. Wt. lbs.
14,500
14,300
14,100
Why does reducing max ZFW enable takeoff weights to be increased?
This is one of many trade-offs made in aircraft design. Wing structure is determined almost exclusively by ZFW under critical gust loads.
What changes are made to the aircraft to accomplish this takeoff weight increase?
We upgraded the wheels, brakes and tires to carry the additional loads during taxi and takeoff.
I have heard that Cessna beefed up the wing and landing gear support structure when the offered their takeoff weight increase on new Citations IIs. Why didn't you?
The reason why Cessna had to make structural modifications was that they increased the landing weight. The landing loads, not the takeoff weight increase, made these structural modifications necessary.
Hardware
Why didn't New Flight increase the landing weight?
Very simply, we did not feel it was necessary. The ability to carry additional fuel, which our STC makes possible, pre-supposes long range flights where landings are made below the existing landing weight of 12,700 lbs. If this were not the case there would be no need for the increase in taxi and takeoff weight. In addition, the structural modifications that an increase in landing weight would have necessitated would have greatly increased the cost of the STC.
Cessna
What effect will this STC have on my airframe warranty?
While we would never attempt to speak for Cessna there is no technical reason for there to be any effect.
Takeoff and Landings
Are there any changes to the landing gear? Landing gear strength is always determined by landing weight, not by takeoff weight or ramp weight. New Flight did not change the landing weight, therefore, a change in landing gear design is not required. Landing gear life limits were reduced by approximately one third to compensate for the heavier loads imposed by taxiing at the higher weight. The reduction in life was calculated using standard aircraft industry formulas, and is fully approved by the Air Transport division of the FAA.
What happens if I take off at 14,500 lbs. and have to land immediately due to an emergency?
If a pilot takes off at 14,500 lbs. and has to land immediately due to an emergency, he would have to land overweight just as in the unmodified aircraft. There is a routine inspection provided in the Cessna Maintenance Manual to accommodate an overweight landing should it occur.
Cessna tells me that they have no responsibility to set new life limits for components or its airframe.
The Citation 11 is a fail-safe design, not safelife. The only structural part that is life limited is the landing gear. New Flight Corporation has the responsibility to set new life limits for the landing gear as part of the STC. These new life limits are set forth in the Flight Manual Supplement supplied with the STC. These new limits are approved by the FAA.
Are the life limits currently set by Cessna valid?
No. New life limits for the landing gear are set by New Flight Corporation in cooperation with the FAA.
Cessna tells me that the structural inspection intervals in Chapter 5 of the Cessna Citation II Maintenance manual are no longer valid for modified aircraft.
This is true anytime an aircraft is modified. The modifier and the aircraft operator must review the maintenance inspection program to determine if a change is necessary. The FAA requires by regulation that an aircraft manufacture provide a recommended structural inspection program. Each operator is required to submit an inspection program and get approval from his local FSDO. The vast majority of operators adopt the manufacturer's recommended inspection program. Should the aircraft manufacturer withdraw the recommended program, he will be in violation of the FAA regulation. Furthermore, the withdrawal will have no effect on the individual inspection programs already approved by the FSDOs.
Has Cessna approved or certified this STC?
Of course not! It is the FAA, not Cessna, that approves and certifies STCs.
Why hasn't Cessna offered an increase in gross weight to the existing fleet as they have now done on new aircraft?
Good question! Cessna heard the pleas of hundred of operators that the aircraft desperately needed an increase in ramp and takeoff weight. They chose to ignore them. We heard the same complaints and decided to do something. We asked Cessna if they would help by providing critical key data. Cessna not only would not cooperate with us, but they threw out obstacles to try to prevent the issuance of the STC. These obstacles caused the program to be delayed substantially and to drive the costs up considerably.
Hasn't the United States Customs Service been operating their Citation IIs at these higher weights for years?
Yes. The Customs Service have been operating a fleet of ten Citations at take off weights of 14,600 lbs. (ramp weight 14,850 lbs.) since 1979. These aircraft have no structural modifications and operate continually in a turbulent low level environment.
Noise
Is there a change in takeoff noise level?
There is an increase in the takeoff noise level to 78.5 EPNdb due to the lower flight path, compared to 78.0 EPNdb. Both numbers are well within the allowable level of 89.0 EPNdb imposed by FAR 36.
Load Factor
Is there a change in the load factor (flaps up)? There is a reduction in the load factor (flaps up) to -1.36G and +3.3 G (from -1.52G and +3.8G). The load factors easily exceed the n-dminimum requirements of FAR 25 Airworthiness Standard, Transport Category Airplanes. For comparison, the Learjet Model 55 is -LOG and +3.OG; the Beechjet Model 400 is -LOG and +3.2G.
How does the aircraft handle at the higher weights?
Our experience is that there is no noticeable difference. We would be pleased to put you in touch with other operators who have purchased the STC and are flying daily at the higher weights.
I am a Part 135 operator. How will this STC affect my FAA approved inspection program?
Implementation of this FAA approved STC will have no effect on your inspection program other than a slight reduction in landing gear component life as called out in the Flight Manual Supplement you will receive.
What performance data will I receive?
A complete Flight Manual Supplement in the same format as the basic manual provides performance data at the higher weights.
For information on this and other modifications available contact New Flight at 303-691-0200.