# IFR?

I have a question about IFR. Right now it is overcast at 600 feet, and IFR. But sometimes it will be overcast at 6,000, and VFR. What makes the difference between IFR and VFR when it is overcast? Is it the thickness of the cloud deck, or what?

Itās all about cloud clearances and visibility. There are different requirements for VFR depending on the class of airspace. In class G, which is the least restrictive, when you are between 1201 and less than 9,999 ft MSL, you must remain 500 ft below, 1,000 ft above and 2,000 ft horizontally away from clouds with at least 1 mile visibility during the day 3 at night. If you canāt do that without doing something stupid, its IFR. Hereās a question for you kid- why do you think it is 500 ft below a cloud but 1,000 ft above? Lets see if you can think like an airman. Read the FARs, or better yet, you should get a Private Pilotās test prep book for yourself. I can tell that you have a lot of interest in aviation and you will learn so much from reading a good prep book where you will find a lot of answers AND get yourself prepared for the written.

I have no ideaā¦

Hereās a clue, ārate of climb v. rate of decentā gettin it?

scribd.com/doc/7589905/VFR-A ā¦ d-Minimums

OK, When a jet jockey pops out of the cloud below you and you are 1,000 ft above the cloud, he has 1 minute to see and avoid you if he is climbing at 1,000 ft/minute, if he is climbing at 2,000 ft/minute he has 30 seconds. Some may disagree, but the consensus seems to be that a decent of 500 ft/ minute is good for airplanes and people so if you fly 500 below he still has a minute to not hit you. Works the other way too, when he pops out of a cloud you will have about the same time.

When itās clear and 100 miles the jet jock will be lucky to see you 1 minute before.

When itās clear and 100 miles the jet jock will be lucky to see you 1 minute before.

Yeah, I know, this stuff is becoming more and more irrelevant. If you can climb at 2000 ft/min you probably have a machine with a traffic alert system and are being vectored away from any traffic with a transponder by ATC. But thatās the theory behind the minimum distances anyway. I think that soon the FAA is going to require that everyone have a traffic alert system of some sort. I think that that is a good idea but I know that there will be a lot of objections because of costs.

Ya know, I was gonna say that (that is the truth) But I figured you would think I was an idiot!(Iām already one anyway)

No Way! Donāt ever say that about yourself. I could tell you about a thousand times I said āDaā to myself when I got an answer. Key is to learn as much as you can and hopefully not the hard way. Any pilot that tells you that they donāt learn something new all the time is either lying or some one you should never fly with.

The rules are written to give some protection to an aircraft flying IFR. Imagine being in the clouds concentrating on the instruments and popping out of the clouds. You would want a fighting chance of looking around for VFR aircraft without running into them 3 seconds later. Hence the distance from clouds and minimum visibility requirements for flights operating under VFR. The speed limits exist for the same reason. More time to see and avoid.

Your local airport, if it is a fairly busy one, requires the lowest ceiling to be 1000 ft or greater AND have a minimum visibility of three statute miles to be VFR. Little podunk airports the minimums are for VFR aircraft to remain clear of clouds and have one mile visibility

TCAS is great. Frank is right, clear and 100 during the day at FL 410, it is amazing the number of aircraft we see on TCAS but never see visually. Youād think 25 tons of aluminum would stick out.

Usually ATC will NOT vector an IFR aircraft around a VFR aircraft. That generally only happens with a real good approach control facility (like Fresno, right Frank?) and only if they have the airspace to move you to. It is easier for them to advise you to level off or change your rate of climb/decent.

If Iām still down in Indian Territory climbing out in my jet and only getting 1000 FPM it is time to start the other engine.
Indian Territory is defined as that airspace generally below 10,000 ft. MSL, populated by lots of Cherokees and Aztecs and all out to get me.

Oh, and our normal rate of decent above 10,000MSL is 2500-3000 FPM and about 2000 FPM from 10000MSL down to 3000 AGL so being 500 feet under the clouds thinking you are safeā¦

John in Saudi

Ok, thanks for all that info!

I would agree that thinking you are safe 500 ft below a cloud, as it relates to IFR traffic, is not a good conclusion. BTW, when Iām on a commercial ACFT and we are decending, I often wonder what the rate is. I thought that they tried to keep it shallow due to pax ocncerns. What is the max that they will do in normal ops, (not an ATC hurry up)? You come down at 2-3 thousand? What are you flying and what do you need to hang out in the wind to achieve that rate, if anything?

Itās actually pretty interesting, Portorjet. The rules on cloud clearances have been around a long time. Wonder if itās time to revisit the minimums given the performance of newer ACFT. Hell, Blackhawk King Airs are climbing at 3,000 ft/min and all those planes with Turbo 550s and the VLJs are all moving fast. Wonder how the airline guys feel about approved single pilot ops in Cessna Mustangs and VLJs, getting up into the flight levels while staring at a PFD most of the time? Not to mention RVS. I know that some Citations are single pilot approved but seems like its opening up to a lot more people. Is the big sky getting smaller?

That is about the normal rate for most jets. I fly a Gulfstream 2 and we normally pull the power about half way to idle while keeping cruise speed (.80-.82Mach) down to the low 30,000 ft. area then transition to 300-310 knots indicated at about 2500 FPM down to 10000 ft. By the time we get to 15,000ft. the power will be close to idle, with idle power used to slow the IAS to 250 at 10,000.
After slowing to 250 the decent is about 1500-2000 FPM depending on the distance left to be flown. At about 15 miles and 4000 feet AGL to go we pull the power to idle, but keep the same decent rate. That starts to slow the airplane. At 5 miles or the outer marker the target is to have approach flaps with the speed at 170 ( full flap speed for the G2) and put the gear and full flaps down. If it is VFR we wait on the flaps until 500 AGL. Keeps thing quieter. Expect for the approach, none of that is with anything hanging out. If you really need to get down, idle power and speedbrakes will hold the same IAS but give more than 4000FPM without being to radical. 5000-6000FPM we do in the simulator while practicing the emergency decent.

Climb is 250 IAS to 10,000 then 300 to .75Mach. Rates vary from 3000 FPM down to 500 depending on weight, altitude and temperature. At fairly heavy weights we average about 1900 FPM for the first 10 minutes.
In a jet when you get to 500 FPM you should probably have leveled off 2 minutes ago. Temperature at high altitudes really has a bad effect, a 1 degree increase will kill that 500 FPM real quick. Kind of embarrassing when you have 300 feet to go. donāt ask me how I know.

The newer jets with more wing need to start down sooner because they will only do about 2000 FPM without using speedbrakes or overspeeding. Pax comfort has something to do with it, but more aircraft performance and optimizing fuel costs.

John in Saudi

Awesome! I think Iām going to fly a little lower from the cloud bases from now on. 8)

See, you should never stop learning.

I see!

OK, let me get something on the right track. If you go below VFR minimums then it is IFR, correct, or no? Give me a yes or no, and the I will go on with my questionā¦