Of course it will happen. And there will be plenty there waiting for it!

I don't think you can get there with the straight wing on a 500/550/560/510/525 Citation.

My CJ2 sim instructor had quite a tale. Landed an F4 on a highway in Texas with bingo fuel. Departed from same highway 24 hrs later. Damn. Waived off first landing due to traffic. Got a ticket from highway patrol too. Fuel remaining was 700lns. They were burning 6lbs a second. Lol. Stud.

Yes. Compare the nm/100lb of fuel. (1) is MCT. (2) is LRC.

About 20% more range or fuel reserve at MCT at FL450 vs. FL410. Makes a difference in a 2.5 - 3 hour cruise leg at 400 kts.

You still win.

Using an Ultra as a reference, starting at MGTOW, ISA, sea level, no wind, using Cessna numbers:

Climb to FL410 takes 706 lbs, 23 minutes, 126 nm distance.

Climb to FL450 takes 885 lbs, 34 minutes, 192 nm distance.

By subtracting the two, FL410 to FL450 is:

179 lbs fuel, 66 nm, or 0.369 nm/lb of fuel during the climb.

To cruise at FL410 MCT those 66 nm will cost you 190 lbs.

So the break even point occurs even before you reach FL450. You are making better fuel mileage in the climb to FL450 than you are cruising at FL410.

Even if you use LRC at FL410, you used 173 lbs fuel. You literally saved only 1 gallon versus MCT climb to FL450 and the better fuel specifics at FL450 will quickly make that up.

Mike C.

The problem with a heavy airplane going directly to 450 is that although it will get there unrestricted, you need to slow too much in the last few thousand feet. Then it takes 40 minutes to get up to speed. (I tried not to get under 200kts IAS in climb above 350)
I've never flown an MU-2, but in the CJ-4 I learned from another pilot who made long legs on a regular basis, to go to 40 or 41, accelerate and after about 30 minutes request a block to 43 or 45, then use about a 200 fpm climb and drift up. you barely slow down and don't need as much time to accelerate back to cruise.
We only went that high for west to east flights, and then only if it prevented a stop.
Speed at 40/41 was 440 .77 about 1200 pph, it would drop to 420 +- at 43-45 1050pph if I recall ...been out of it for a year.

This was a flight of three. Lead guy got in. My guy was second and saw nothing at 150feet. The third guy missed too. So they were headed to alternates with really not enough fuel to get to them. Hmmmm. I asked why didn’t you just continue to descend like it was a glassy water landing in a sea plane? You were 150ft AGL from a big runway with emergency equipment! He said...too risky...we just were going to climb out and eject when we ran out of fuel.




Ok. Never mind.


Good to have options.

Yes, but could he climb direct to 450 and then eject?

Ha. No. Coffin corner. That plane was at risk.

The reality is they used to put them in after burner and go straight up to 90,000. Basically a ballistic missle. The last 30k or so was with engines shut off. They would essentially drift back down and relight under something like fl40.

Don’t think coffin corner was an issue.

The Ultra book says climb speed at FL450 is 163 KIAS.

Cruise speed at FL450, MCT, 15000 lbs weight, is 174 KIAS.

It takes 40 minutes to accelerate 11 KIAS? Doesn't feel like it would take that long.

Granted the Ultra is a lot better at this than a straight V.

Mike C.

I was talking about the CJ4 that I flew.

The point I was trying to make was that book numbers don't just appear, sometimes it takes a while to accelerate.

Have you been there...?

I get that, but the climb concludes at 163 KIAS (356 KTAS), and cruise at heavy weights is 174 KIAS (378 KTAS), so it doesn't seem like there's a great gap to overcome, 22 knots true.

At 1G, 15,000 lbs, FL450, the buffet onset is mach 0.52, 135 KIAS, 298 KTAS, so you are quite some margin over that at 163 KIAS. Would that be "mushy"?

These figures from the Ultra manual.

Mike C.

I never got that slow in climb in a CJ4, (I only have limited right seat time in an Ultra).

Maybe it is just pilot error.... I preferred speed over rate, still got to 400/410 in about 22 minutes.

I'm retired now anyway...

EDIT: I just visited your website. I understand that there is nothing there that I could possibly understand,".
I can now see why only hard numbers mean anything to you...no gray zones for engineers.

Got a tour of the King’s Falcon 10.

John likes 450. Martha prefers 410. :D

Hot wing!