sfzpilot

Hey guys and gals,

I am an instrument pilot who was flying with BOS_CTR in the Cherokee a a few weeks ago. I heard something like this: Callsign, descend to cross 35 Miles NW of the MHT airport at and maintain 11,000. I was just wondering, do the FMC's cross a DME or do guys create a fix which is defined by the 35 DME? Or do you guys use pen and paper like the old days?

Thanks so much!

atlmsl

Good old FMS. Create a point 35 miles from MHT and program the altitude. The CRJ will give you the vertical speed needed to cross the fix at said altitude.

USMCFLYR

I often get this type of crossing restriction coming into ABQ. I know where I am in relation to the airport (using a wypt for the airport) and make sure that I am at whatever altitude they assigned prior (basically pen and paper like you say). The trick in my airplane comes from the descent profile. Do I figure out a nice long near idle descent or just dive and drive at the last moment? Hummmm....decisions, decisions. I can't wait to get my hands on some of that descent profile FMS type stuff those fancy airplanes have in them!

USMCFLYR

boilerpilot

Either do the mental math of 3 miles per 1000 feet you need to lose (an approximation for jets), or you can program the fix into your FMS. Generally, you have KMHT in your FMS, and you do something like "KMHT//35" or "KMHT/-35" and that will create a fix for you 35 miles "this side" of KMHT, which you can then assign 11000 to. After that, the FMS will tell you what descent rate you need to get down, and generally a "glideslope" too for you to monitor your progress on.

andy171773

good ol north central ey?

i got my commercial single there..did all my training outta EWB

but yea

You just program it in from KMHT for the airport (just putting MHT would be the VOR) and viola

you can even make a green 35 mile ring around the airport!

oh technology...

coldpilot

You guys are spoiled. Gotta love doing the mental math to make it in a /A! Real pilots don't need an FMS

johnnysnow

I did my 1st solo x-country to North Central...Ahh memories.

marco

You can also do the mental math another way if you like to hang at your cruise altitude until the last second and know the performance of your airplane and the time that you should cross the fix:
a. determine altitude to lose
b. determine the descent rate you want to lose that altitude to make the crossing and convert to minutes
c. start your descent when you are that many minutes away from the fix

ex: cruise altitude is FL310, crossing restriction is 35 out of MHT at 11000 = 20000 feet to lose. I want to descend at 5000' per minute: 20/5=4 minutes. -Start my descent 4 minutes out.
-Cruising at 400kts is roughly 7 miles per minute, multiply by descent time: 7x4=28 and add to 35 (crossing fix): 28+35=63. (round up for fudge)
-Start descending at 65 miles out of MHT at 5000'/min maintain your cruise airspeed.

Now if ATC gives you an airspeed restriction while you're in the dive, you're not gonna make the altitude at the fix. Maybe I do need pen and paper for this one!!

usmc-sgt

No mental math here on the Universal FMS.

1. Select Vnav
2. Enter MHT
3. Enter a - or a + and then the distance on this side or that side of the fix in this case +/- 35
4. Enter the desired descent rate
5. Select VNAV on the FGCP
6. Watch the magic

USMCFLYR

This is what I meant in my post - I just didn't do as good a job of explaining it obviously I've not had a airspeed restriction in the dive. Does this happen often? I have had to work with ATC often to stay higher longer than they expected because they try to descend me on a more typical airliner profile; but usually they are most accommodating.

USMCFLYR