KerbalX

The C-21 on display in the SPH.

• I included the aka in the craft name so people who know this plane under its civil designation can find it.
• At first, I used two Mk1 crew cabins in order to make the plane look like its real-life namesake. However, that (and the landing gear setup then) resulted in the plane being too nose-heavy for takeoff. I then clipped two more Juno engines to add more thrust; while that helped, the plane was still nose-heavy after liftoff. So, I removed one of the crew cabins and drained the rear NCS Adapter. I still got a wobbly takeoff, but at least it could fly smoothly if it got off the ground (in one piece, that is). The real-life Learjet 35 was nearly as long as a North American Sabreliner anyway.
• I remember that my T-39 Sabreliner and my Jetstar replica performed terribly with just two Juno engines, so that was another reason to clip two more.
• The landing gear was tricky to add at first, since the wings were positioned abnormally. Even with the plane’s nose-heavy problem addressed, it still got slip-and-slides for takeoff runs. To make the landing gear straight for sure, I added them to the bottom of the fuselage and moved them out as far as I could - but that wasn’t enough. So, I added 1x1 Structural Panels to the bottom, attached the landing gear to the far ends, hid the panels in the wings, and moved them out. It was then smooth takeoffs from there.
• The real-life Learjet 35 had a drag chute, so I installed one in the back.
• Since this was a business jet as well as a small cargo or patient transport - and was assigned to theater commanders outside the continental United States - I included nav lights. You’ll have to use the AG3 button for them since they’re not linked to the regular light switch.

After the final (major) design changes were made, the C-21 took off from the KSC without any problems and headed north.

• The only changes made afterwards were to the cargo (as in what went in it), the wing paint job, and the antenna on the top of the fuselage.
• Despite having four Juno engines for thrust, I didn’t want to take the chance that it would be unable to climb Alt Test Mountains - or run out of fuel in the middle of the ocean. So, I had the plane fly north for this test cruise.

The C-21 flying along the countryside. The cruise did experience some fluctuation in altitude with MJ aircraft autopilot on, but it stayed within 30 meters of the selected cruise altitude once settled.

Although the C-21 had reached a sufficient altitude to have flown over Alt Test Mountains, it had already spent a few minutes flying north and there was still no guarantee it would be over or within gliding distance of dry land when it ran out of fuel. So, it continued to fly north. If it can go over Alt Test Mountains, it can certainly go over that mountain range to the north without any problems.

• I haven’t decided on a name for that mountain range yet, and Alt Test Mountains Two (or Junior) sounds too cheesy.

750 km away, 55 minutes since takeoff, and 10 fuel units left. It was time for the C-21 to begin its final descent.

• It’s a good thing the plane could glide all the way to the edge of the ice cap, or the pilot would have been in big trouble.

Unnamed pilot on Kerbin’s northern polar ice cap after a smooth landing. Now he can collect his ice samples for his research - and then wait for a fuel truck to fill up his plane since his tanks are nearly empty.

Drag chute test at the KSC.

• Just like the real-life Learjet 35, this aircraft came with a drag chute to reduce the landing distance. Works best when landing gear brakes are on as well.