Hahah .. I like your technique!

TheSultanofScud, thanks for making me realize I need glasses. thank you

But, about ATC I say, "DO YOUR JOB!" If they don't have time for it, just say "unable."

But I do agree, as the airspace gets more crowded, these things will be gone.

Even if you can fly the pen your aircraft may not like it- if piston, shock cooling and pressurization issues. Even some jets and turboprops may not like the power setting vs. pressure reqm'ts- especially in icing if you have to carry power- I'd done some in DC-9-32F medevacs and the icing reqmt for bleed air/power would put you behind the pen. You'd best figure out in your performance chart/manuals if you can do 1000' per NM at speed or greater before trying one.

I'd never consider doing anything of the sort in a recip.

I agree with the caution...I know a lot of people in my line of work don't believe that descents kill turbines, but I'm a big believer that the affects of extreme rapid descents are cumulative...bottom line: no matter what flavor of powerplant, the metal doesn't forget. Even if I'm wrong, I figure the conservatism will only help to keep this 'ere noob from smoking an engine or bending someone's ride.

I think it would be interesting to try one of these approaches in a civilian jet or turboprop that could be slowed enough to keep up with the profile. The fact that you could run into problems in a DC-9 puts things in perspective, though. I understand you had power requirements to run your bleeds, but all the "there I was" stories from DC-9/C-9 guys I've met boast about the plane's ability to come down like a brick. Definitely gives me a frame of reference.

I agree with the earlier posts regarding ATC...if the request didn't give them extra sweat and tears, I'm sure it would have them scratching their heads and chuckling.

Thanks for all the great posts! The learning curve is getting ironed out.

In the KC-10, we typically can get 750'/NM for a descent (speedbrakes, gear, slats). If you really need to get down, you can configure with flaps, slow down, then push over, and as you accelerate, you clean up the flaps, extend the speedbrakes, and go to the slat extend speed. You will drop like a rock. Then the only concern is slowing down to get the flaps back out.

-Fatty

The approaches have changed now - but NAS Jacksonville (FL) used to have a HI_TACAN approacg to Rwy 27 that started out south of the field and proceeded inbound and then arced to the west around the field at 7.5 NM with step downs and hard altitudes if I remember. We use to take students there on the 2nd flight in the airplane. We would start off with the very easy straight-in HI-TACAN to Patrick AFB and then go to NAS Jax. It was quite the eye opener!

Tweetdrvr - I hope the TCNs at Ellington don't go away soon. It is about our only way in there and we use it all the time! I helped getting the TCN into Millington, TN and Savannah Intl. All places that we operated out of regularly but have no approach that we USN/USMC tactical aircraft could use since we are not up with the rest of the civilized world!

USMCFLYR

The Historical reason these even exist (other than student harrassment for pilot training) is to get a long-enough flight path to allow high flyers to descend between competing pieces of airspace to their destination.

After all, wouldn't the easiest answer be to just give a guy at FL240 a straight-in that starts 75 miles out?

But, there are usually obstacles in the way: MOAs, Artillery ranges, Victor Airways and Jet Routes, some other airport's Class B, C, or D, International boundaries (a big one in the corners of countries in Europe), etc.

So, they build things with radials, arcs, and more radials, in an effort to squeeze the required distance into the available space for an approach, and go around or between the obstacles.

I read once, many years ago, that a High-Approach may have a maximum descent gradient of 10 degrees outside of the FAF, while low altitude approaches may have a maximum of 5 (without a waiver for either). I believe that is correct.

Fighters can often do 13-15 degrees nose-down and not accelerate (Idle/Boards), and if you need to get down, just lower the nose and go fast--it's impossible to exceed the redline. Fighters usually have waivers to do 300 to 350 kts below 10,000 in peacetime.

But airliners are actually much cleaner aerodynamically, and the most I could do in the A-320, 727, or even the Lear 35 was about 4 or 5 degrees, even with idle/boards. Sultan, starting speed isn't the issue--in fact, the faster you go, the more energy you can lose (drag going up with the square of velocity, and power required (or lost) going up with the cube of velocity).

I don't think "Feet per minute" or "Feet per mile": I think "Degrees nose-low," which is a constant, regardless of speed. (I'm talking flight-path angle, not ADI pitch, which will change with speed).

Correct. My platform's usual descent profile is idle/boards OUT and 12 degs nose low to hold 250 for the high penetration approach until some point on the approach (depending on requirements) or "platform (5K') at the boat - then it is idle/boards IN and 5 degs nose low - still maintaining 250 kts.

USMCFLYR

How do you determine "Degrees nose-low"? Are you talking difference in pitch from level flight? Also, when looking at an approach plate and thinking of terms of degrees nose-low, how do you determine if you have the performance to fly the procedure?

-Fatty

KC10:

It's all a part of the 60:1 stuff they tried to teach me 25 years ago, but I didn't learn to apply it until a few years later.

The formula is (Change in Altitude) / (Change in Miles) x 10 = Degrees required.

So, if the IAF is FL240, and you have a hard crossing altitude of 3000 ft 35 miles later,

21 / 35 = 3/5, which is .6. Multiply by 10, and : 6 degrees.

(The hard part is figuring the miles when it is part radial, part arc, which still requires 60:1 rule stuff of 1 degree= 1 mile at 60 miles, and fractions thereof). So, I make the kids do all this math during the brief, and I have them write the gradients on the plate...makes it a lot easier to fly than doing math-in-public at 400TAS.

This used to be easy to teach, but I have found in the last 4 years, none of the kids are any good at multiplication tables. Apparently, in order to pass standardized elementary school testing, all children are issued a cell-phone to use as a calculator.

As to performance: in the F-4 and T-38, we had specific pitch and power settings that gave commonly used descent angles. Later, I figured out those angles in the Lear 35. In the T-38:

Idle 300 kts Clean 7 degrees
80% 300 Clean 5
80% 300 Boards 10
Idle 300 Boards 13

The kids are taught these in academics.

300 kts = zero pitch on the ADI, so angle=what you see on the ADI. However, the jet now has a Flight Path Marker, and you can use that to fine-tune actual descents, if doing speeds other than 300 kts.

Finally, since the only speed restriction above 10,000 is usually to stay subsonic, if a student discovers he is very high because he started down very late, he can just dump the nose 20, 30, even 40 degrees, idle and/or boards, and let it do 400-500 kts.

They never think of that, though...that suggestion usually comes from the other cockpit.

Ok ... you're doing the same we do. I thought perhaps when you said "no ADI" and "flight path angle" you had some new method.

DC-10
Idle Power = 300 ft/NM or 3 degrees
Speedbrakes = 150 ft/NM or 1.5 degrees
Gear = 150 ft/NM or 1.5 degrees
Slats = 150 ft/NM or 1.5 degrees

So, the max you can achieve is 7.5 degrees nose down from level flight or 750 ft/NM.

There is a technique of using Flaps 22 (No speedbrakes), which will give you the same performace but you have to be below ~220kts. The benefit is that you are just one step (Flaps 35) from a landing configuration.

I agree with you 100% about our eductional system and the "new math".