|
CITATION II and Citation S/II WITH CLIFFORD FJ44-3A CONVERSION
Updated: October 6, 2008
Q. Isn't there already a Williams engine STC for the Citation II?
A. No. At this time, there is no Williams engine modification certified for the Citation II. Our project is active with the FAA. Our certification airplane is in flight test in Mojave, California.
There are, though, two Williams engine modifications certified for the Citation I sold under different names, which have lead to some confusion.
^ TOP
Q. I understand that the projected performance of your company's modification of the Citation II with Williams FJ44-3A engines calls for an 18 percent reduction in takeoff runway requirements. I am concerned about landing distances/stopping distances on a contaminated runway. I do not understand how you can remove thrust reversers and still project a reduced runway requirement.
A. Good question. The answer is the difference in the idle thrust of the P&W JT15D-4 and the idle thrust of the Williams FJ44-3A.
The P&W JT15D-4 engine at ground idle produces approximately 450 lbs of thrust. In fact, the idle thrust of a JT15D-4 engine is 18 percent of its takeoff rated thrust. When a JT15D-4 equipped Citation II or S/II lands or rejects a takeoff, each engine remains at the 450 lbs idle thrust. This means that there is a total of 900 lbs of thrust pushing the airplane. On a contaminated runway, T/Rs can make a difference. However, it is important to note that takeoff performance charts do not make any allowance for T/Rs.
The Williams FJ44-3A engine has a ground idle thrust of only 125 lbs of thrust. The FADEC system is linked to a squat switch that senses weight on the landing gear and schedules the engine to an absolutely minimal thrust level. As a result, ground idle for the FJ44-3A engine is only 4 percent of the takeoff rated thrust.
The Williams FJ44-3A engine's minimal ground idle thrust, along with installation of BFG heavy duty brakes allows us to remove T/Rs, reduce over 250 lbs of aircraft weight and still reduce stopping distances and runway requirements.
It should be noted that Cessna has taken advantage of this capability and eliminated thrust attenuators from the CJ3 design and removed them from the CJ1+ and CJ2+.
^ TOP
Q. How many conversions do you have to sell before you begin engineering?
A. Clifford Development is fully funded to complete the STC for the Williams FJ44-3A conversion of the Citation II. We are not dependent on conversion sales to complete the STC for the Citation II. Additionally, we are also funded for the certification of the Citation S/II with Williams FJ44-3A engines and both engineering programs as well as company flight testing are complete.
^ TOP
Q. When will the Citation II and Citation S/II engine conversions be certified?
A. Both will be certified in early 2008.
^ TOP
Q. If I buy your Williams engine conversion for my Citation II, what support will I get from Williams International on the FJ44-3A engines?
A. Williams International provides full warranty support for the engines thru its existing and new Clifford modification service facilities. Each new owner will receive Williams’s factory training as part of the modification package. In addition, Williams International offers the widely acclaimed Total Assurance Program (a power-by-the-hour) for these engines as well. Full details are available at http://www.williams-int.com/tap.html.
^ TOP
Q. Will I have to keep my old ribbon engine gauges or will I have to pay extra for digital instruments?
A. Our kit for both the Citation II and S/II includes a new Ametek digital engine and fuel display, along with the relocation of the annunciator panel into the glare shield. The Ametek display is similar to the ones used in the current Citation Bravo and Excel aircraft.
^ TOP
Q. What other changes are being made to the airplane as part of this STC?
A. More than 36 major improvements are being made to the airplane including….
1. New Williams FJ44-3A Engines @ 3000 lbs thrust with 4000 hr. TBO (thermo-dynamic thrust flat rated at 2820 lbs for takeoff at sea level, 79 degrees Fahrenheit)
2. Lower ground idle speed for quieter, more efficient ground operations
3. Shorter landing distances without T/Rs due to lower idle thrust: 125 lbs per side vs. 450 lbs on JT15D-4
4. Full Authority Digital Engine Control (“FADEC”) for “fly-by-wire” engine control
5. Dual FADEC Airdata sources added
6. Dual ignition exciters on each engine, JT15D has only one
7. Engine sync is electronic with no mechanical parts to maintain
8. New Ametek digital engine display: Fuel, RAT (ram air temp.) and standby N1
9. New LED annunciator panel moved to glare shield
10. Heavy duty BFG brakes, new wheels and tires
11. New bleed-air inter coolers and control valves designed to handle the FJ44-3A
12. No major structural modifications required, uses the existing factory engine beams
13. FIU (FADEC Interface Unit) are mounted and interchangeable
14. More mass airflow for better ACM spool-up and heat at altitude
15. Mach warning box removed and replaced with digital controller
16. Gear Warning based on airspeed not Power Lever position
17. Micro Switching removed from power levers, now all digitally controlled
18. New larger center pedestal can hold A/P components and 2 FMS size controllers
19. Throttle quadrant moving parts rebuilt to overhauled standards
20. Starter/Gen cooled with fan bypass air - increased life on S/G brushes
21. Carbon Fiber aft cowls
22. FADEC System certified to new July 2007, P2T2 Standard
23. Removal of Peri-seals to more reliable bellows seals within engine compartment
24. Same size fuel and hyd fittings changed to AN and MS so lines cannot be crossed
25. New low-maintenance sealed lead acid battery (Hawker 44ah battery included)
26. Improved Instrument panel cooling for longer component life
27. New current technology Fuel Flow transmitter
28. New E/L and instrument panels as required (no patched instrument panels)
29. New quick donning O2 masks for the cockpit, for a service ceiling increase
30. Removal of EPA equipment, requires lower maintenance
31. Pylon skins increased to 0.032 for longevity
32. OEM aluminum S/G cables replaced with copper for better starts
33. Installation configuration allows for an average 2.5” forward CG shift
34. STC designed to be installed as a kit by others, all part approvals, installation instructions, Flight Manual with new performance charts for Continued Airworthiness included
35. Flight Testing performed by industry recognized professional test pilot organization with computerized data acquisition, allowing real-time performance charting and accurate Flight Manual supplements with new performance charts
36. S/G ground point relocated to reduce corrosion and grounding issues
^ TOP
Q. I understand that the bleed-air from the Williams FJ44-3A engine is of a higher pressure and temperature than my current JT15-4D. How will this affect my aircraft?
A. The temperature and bleed pressure run higher in the FJ44-3A engine. We have redesigned the inter-cooler and use a new style shut-off/regulator valve to handle this. This design is similar to that on the Cessna CJ3, which has the same model engine installed. The air cycle machine spins up faster on the ground, which will assist in cooling and help extend the life of the air-turbines bearings. The engines also provide higher mass airflow increasing the cabin air volume, which will significantly improve cabin temperatures at altitude and improve pressurization flows.
Based on the available bleed air, we anticipate certifying both the Citation II and S/II to higher altitudes in a separate STC. In anticipation of that additional certification, we are installing quick donning oxygen masks as part of these initial STCs.
^ TOP
Q. How much credit do I get for my old engines?
A. Hours remaining on the engines greater than 500 hour to overhaul are given an additional credit of $40/hr.
^ TOP
Q. I have a question about the reported takeoff thrust of the Williams FJ44-3A engines.
A. The sea-level thermo-dynamic thrust rating is 3000 lbs for the Williams FJ44-3A and 2500 lbs for the P&W JT15D-4 at 59 degrees. However, the Williams FJ44-3A has a de-rated takeoff thrust of 2820 lbs per engine at sea level and 79 degrees Fahrenheit. This is the flat-rated thrust used for all sea-level temperatures below 79 degrees.
Regardless of temperature, during the climb to altitude, the engines have an extra 180 lbs of performance margin based on the flat rating on this engine that is designed to deliver 3000 lbs of thrust.
All performance projections supplied by Clifford were developed by Williams International using 2820 lbs of thrust.
We apologize for previously incorrectly reporting these engines as 3000 lbs of takeoff thrust.
^ TOP
|
