Anyone flying a CJ2? I am curious about hot and high performance and realistic cruise speeds in the summer.

Thanks,
Steve

I manage and fly a few as well and buy and sell them. Short answer: depends. Much better than a straight CJ but depends on your mission. Are you trying to take off high and hot and go 1200nm? Won't work.

If you give me some specifics I'll try to help.

-The Citation Jet Exchange

Thanks Corey. I am interested to know what the max temperature you can leave from an airport at 6100ft (KCOS) at max gross is and make first and second segment? Also, what do you plan for realistic cruise in the high 30s?

Thanks,
Steve

Steve,

Using the 6000 foot numbers, flaps up takeoff (better second segment climb but more runway required) 0 wind numbers:

MTOW 2nd segment climb gradient, single engine:
20C: 3.5
25C: 3.0
30C: 2.2
35C: 1.5
40C: .7

Leaving off 700bs for a takeoff weight of 11,800lbs
MTOW 2nd segment climb gradient, single engine:
20C: 4.2
25C: 3.6
30C: 2.8
35C: 2.1
40C: 1.3

Using flaps 15 would severely restrict 2nd segment climb on days above 20C at MTOW, but for data purposes flaps 15 MTOW you'd need 5240 feet of runway at 20C and the chart only goes up to 25C for max temp allowable at MTOW with flaps 15. At 11,800lbs 30C you'd need 5570ft of runway.

If it is a warm day I'd recommend flaps 0 for the 2nd segment radiant (it will be required as I noted above).

Flaps up 6000 feet MTOW Runway Required:
20C: 6250
30C: 7860
33C: 8600

Flaps up 6000 feet 11,800lbs Runway Required:
20C: 5670
30C: 6650
35C: 7330

You shouldn't have issues with the long runways at COS, on exceptionally warm days you will need to leave 700-1000lbs off.

The CJ2 will NEVER have an issue flying in the high 30s under any weight/temp. FL 400 and FL 410 are my standards for any medium-long range flight. You'll hit mach .72 (Mmo) at all conditions and need to throttle back in the high 30s and you'll get a TAS of 400 to 420 depending on OAT. Fuel burns will be higher in the 30s at 800-900pph vs low 700s to low 800s in the 40's.

When I'm heavy and it's warm (ISA +5) I won't go directly to FL 430 or FL 450 although it can go right to 430 if you're patient. Again it depends on temperature. If it's ISA to ISA- you'll accelerate quick to Mmo at FL 400/410 and your TAS will be 400-415. If it's ISA+5 or greater it may take a little while to accelerate depending on weight to .72 Mach when you hit the redline TAS can be 405-420.

Remember TAS is a product of Mach which is affected by OAT. The colder the temperature the slower mach is and slower your TAS is but you'll have greater performance.

After burning a little weight I can go to FL 430 or FL 450 if I need to get above weather or stretch fuel where you'll see 390 to 405 TAS. Usually 400TAS is a good flight planning number for any altitude/temperature.

-Corey

Corey, thank you for all of the detailed info and taking the time to answer everything so in depth!

Thanks,
Steve

You're welcome. Here's a pic from a delivery I did in a CJ2. FAT-PCD for prebuy, about 1450NM, 3:30 flight, landed with 1300lbs. 800lbs total per hour, 403 TAS at 41,000 on an ISA +3 day.

Corey, In the summer, St.Louis, mid weight, what would be your take off roll distance on average in the CJ2? Thanks, Jeff

I've thought about this a lot and I don't have a definitive answer. I would say around 2000 foot ground roll with those conditions. I'm usually single pilot departing on a 7000ft runway and not paying too much attention. I'm typically closer to mtow than mid weight. On a cold day I rotate around 1000 feet, nothing sticks out as far as being a runway hog at low altitude on a hot day at mid weight.

Thanks Corey

Roughly speaking, take the book takeoff distances and subtract 1000 ft for the ground roll.

Works for landing as well, about 1000 ft less than the book numbers.

Mike C.

- 50’ at the threshold.
- 3° glideslope.
- 50’/sin(3°) = 955’, rounds to 1000’.



(Just supporting evidence for your rule. )