When do you start your descent to circuit height

[elslicko1]

OK, here is a pretty basic question so forgive me for sounding stupid.

After being cleared to enter into controlled airspace, not about 2000 feet VFR, when do I start my descent to the circuit height of 1000 feet? Is it immediately after I enter into controlled airspace or do I wait until I’m nearer the airfield?

[BackPacker]

If you're cleared "not above 2000 feet" then it's completely at your own discretion. You can descend immediately, or when you're close to the circuit, or simply set up a shallow descent to arrive at the proper height when joining the circuit.

Of course you've got to abide by rule 5 (land clear etc.) but that's rarely an issue.

If you want to know how the pro's do it: Take your altitude to descend in 1000's of feet, multiply by 3 and that's the amount of nm out you start your descent. So to descend from, say, 7000' to 2000' takes (7-2)x3 = 15 miles. And your rate of descent required is then 5 times your groundspeed in 100's of knots. So for a 100 knot groundspeed, your descent rate is 500 ft/min.

Which is very convenient because that's about the maximum that you can do in an unpressurized aircraft without passengers being uncomfortable with popping ears and such.

[1800ed]

Do you mean 'not above 2000ft VFR'? If so, you have been cleared to fly within that airspace at an altitude below 2000ft. So you could descend whenever you like with that clearance.

[Pitts2112]

Of course, if you're doing it properly, you'll have to CLIMB to circuit height! :E

[Big Pistons Forever]

If you want to know how the pro's do it: Take your altitude to descend in 1000's of feet, multiply by 3 and that's the amount of nm out you start your descent. So to descend from, say, 7000' to 2000' takes (7-2)x3 = 15 miles. And your rate of descent required is then 5 times your groundspeed in 100's of knots. So for a 100 knot groundspeed, your descent rate is 500 ft/min.

Which is very convenient because that's about the maximum that you can do in an unpressurized aircraft without passengers being uncomfortable with popping ears and such.

Actually "the Pro's" take the number of thousands of feet difference between the current altitude and the circuit altitude and then double it for a 500ft/min descent. When the GPS or DME time to go gets to this number it is time to trim for a 500 ft min descent. (eg 5000 ft to descend = start to descend at the 10 min to go point).

Personally I just wait for the "VS required" display field on my Garmin 495 to get to "500 fpm" and then start down:ok:

[Tinstaafl]

I do the same. Garmin's vnav makes it sooo easy! I also use the ETI to reduce power: I know what MP I want to have in the circuit so I set inches of MP-above-circuit power to match minutes-to-go. As the minutes tick down I reduce MP accordingly. Extend flap & gear at the right times as I join the circuit & I usually don't have to adjust throttles until closing them to land.

In the Kingair 200 though, I use the common 3 x height rule of thumb. In PA31's I could use 5 or 7 x to give about 500'/min at reasonable power settings but that still left me having to judge power reduction timing. Using minutes to go does both.

As for the original question: Cleared 'not above' so operate at your discretion anywhere below that altitude while conforming to any min. height rules.

[FREDAcheck]

What the pros do in multi-engine planes is not necessarily best advice for a single. Typical glide figures for a light single will be about 600 feet per nautical mile, or about 900 feet per minute of you're doing 90kt. I go for something closer to that (say 500 feet per mile), if there are no other constraints (such as ATC direction, or local procedures). So I start descending from 2000 feet to 1000 feet about 2 miles from where I want to join the circuit.

[FlyingStone]

It depends mostly on the aircraft actually. Most times, I plan to make my descent with 500 fpm rate of descent and the speed is usually 10 knots above cruising speed. To make such descent, I divide difference between current and target altitude (say traffic pattern altitude) and multiply it by amount of miles I'm doing over ground during the descent in each minute. If you're flying a very aerodynamic aircraft (or aircraft which requires slow decceleration in order to prevent shock cooling), I would recommend adding one minute for deceleration at traffic pattern altitude.

So in practice, it looks like this: you are flying at 8000ft and airfield is located at 500ft. The normal procedures call for traffic pattern at 1000AGL, so the traffic pattern altitude would be 1500ft. We then get the difference of altitudes, which is 8000-1500 = 6500ft. Let's say our groundspeed during descent is 120 knots, which means we are covering 2 NM of ground track each minute. If we want to maintain rate of descent 500 ft/min, we should be descending for 6500/500 = 13 min, which then means we will cover 13*2 = 26 NM of ground track during our descent. Adding one minute for deceleration, this becomes 28 NM, which I usually round up to 30 NM, since only the best pilots (with myself not being one of them) can begin their descent at 28.00000000 NM from the airfield and maintain 500.0000 fpm during descent :)

[DX Wombat]

I was taught that you make an overhead join at 2,000' on the airfield QFE then descend to circuit height deadside unless the airfield has differing requirements,

[FREDAcheck]

I was taught that you make an overhead join at 2,000' on the airfield QFE then descend to circuit height deadside unless the airfield has differing requirementsSo was I, but I tend to ask on the radio what the norm for the airfield is, and do that.

Cue long and tedious thread drift into the merits of OHJ.

[Local Variation]

We have this same restriction at my airfield.

For a SEP in this scenario, you should consider a number of things and it is mostly about experience and common sense rather than juggling numbers. (such as descending over a built up area, descending into wind or with the wind, too name but two.)

That's how I and many others I know learnt to fly VFR in and out of a busy field through 2000ft CAS restrictions.

Quoting figures of 500ft/min is all well and good, but he's not vectoring and intercepting the ILS at 8 miles is he ?

[mad_jock]

I do wonder with some airfields who use this 2000ft limit how an SEP can get in and still comply with the glide clear requirement.

Same with quite a few instrument approaches which people seem to be quite happy doing in a SEP

[spekesoftly]

Cue long and tedious thread drift into the merits of OHJ.

Most, if not all, UK airports inside Controlled Airspace do not normally permit OHJs, nor do they have a "deadside". Circuit direction can be simultaneous left and right hand, as directed by ATC, and they will give specific instructions to joiners.

[Genghis the Engineer]

Most, if not all, UK airports inside Controlled Airspace do not normally permit OHJs, nor do they have a "deadside". Circuit direction can be simultaneous left and right hand, as directed by ATC, and they will give specific instructions to joiners.

Really? How fascinating.

OHJ's aren't common, but usually permitted in my experience, and similarly most airports whilst they may prefer not to see aircraft deadside, don't prohibit deadside joins, go-arounds to deadside, or a descent deadside if the join was overhead.

Some UK airports don't permit OHJs or deadside joins. Simultaneous left and right circuits are fairly unusual, although do occur.

G

[fireflybob]

One important aspect is to be level at the circuit height before entering the live part of the circuit - otherwise you risk descending on top of an a/c which is already in the circuit.

Applies to OHJ and "commercial" joins

[The500man]

I was taught to set QFE and descend to circuit height when first visual with the airfield. Then again it's unusual to go above 2500 amsl in my area.

I usually check the Pooleys guide since it normally has the recommended joins listed, or call for a briefing.

A 500 ft/min descent many miles out won't do you much good if you're engine quits!

[Piltdown Man]

Work backwards (in your mind, when flying - so no stress then!) from where you'll want to be when you turn base. By this I mean altitude, speed, power and configuration. (I'll be got at here, but in something like a 152 this has little relevance apart from height. All the speeds and power settings appeared to be the same.) First of all, you'll have to lose 1,000 feet. At something sensible like 500'/min that will take two minutes. What will be your groundspeed as you join the circuit? If it's 120 knots that will take 4 nautical miles. And you will need to slow up a but, so allow a minute for that. So, when you reckon that you are approaching "half a thumb" away on a half mil chart, ask for a descent. Set the appropriate power and you're done.

PM

[Jwscud]

I do wonder with some airfields who use this 2000ft limit how an SEP can get in and still comply with the glide clear requirement.

Same with quite a few instrument approaches which people seem to be quite happy doing in a SEP

You are exempt from the Low Flying Rules under the ANO as follows:

6. The exemptions from the low flying prohibitions are as follows—
(a) Landing and taking off
(i) Any aircraft shall be exempt from the low flying prohibitions in so far as it is flying
in accordance with normal aviation practice for the purpose of—
(aa) taking off from, landing at or practising approaches to landing at; or
(bb) checking navigational aids or procedures at,
a Government or licensed aerodrome.

Certainly covers the second case of Instrument approaches and most likely the first. Whether it's necessarily wise is another matter...

[mad_jock]

Aye but thats intended for inside the ATZ it not meant for you to fly :mad:ing miles from a VRP over the middle of a city.