How accurate is your Mode C?

[BackPacker]

As to accuracy of the transponder, when the QNH is close to 1013 I can read the flight level against altimeter; I believe the 25' accuracy statement!

My usual aerobatics height band is between 3000' altitude on the local QNH, and FL55. I leave the altimeter on QNH, and read the FL from the transponder. Works fine. You just have to keep in mind that if the QNH is < 1013, the height band available might be (significantly) less than 2500'.

My only suggestion is to ask if you kit-out with a radio and talk to the LARS service?

A lot of gliders have a radio but do not have their FRTOL. So they're only allowed to operate on specific glider frequencies. That rules out getting a LARS.

[Mark1234]

Originally Posted by SNS3Guppy

ATC needs me to descend. They ask me to keep my speed up and give my best rate of descent. You're operating near the "edge" of the airspace, and think that means something to me or ATC. I deploy the speed brakes and pull the power to idle. I'm doing 250 knots and descend into you from behind, with a high rate of descent. I'm going faster than you think, descending into you at several thousand feet a minute. Even if the altitude to which I'm cleared is the bottom of the controlled airspace in that area, if you're right on the "edge," and if your altitude isn't quite correct, it doesn't take much error, especially with a closure rate of 250 knots or greater and several thousand feet per minute vertically, to wind up with a collision.

I'm departing. I'm heavy, so I'm not climbing as fast as the controller might like. I get a turn away from other traffic, and continue my climb. You're flying with your transponder off, or perhaps have it on, but elect to do so on the edge of a busy terminal area, thinking that it's a good idea so long as you're on the "edge." During departure, I'm busy getting cleaned up and configured for the enroute climb, and I don't have a really great view of other traffic, especially at our climb speeds which may be closer to 300 knots, even below 10,000 (minimum safe speed allows higher than 250). I may be on a vector, and I may pass in and out of controlled airspace during that climb. The controller may make a mistake. Why put yourself in the position of being in a traffic conflict in the first place; it's not safe for either one of us.

Accepting there are undoubtedly reigonal differences, in Australia (and allegedly the UK, though I can't find a reference), if you are in controlled airspace, a 500ft protective buffer to the base is maintained; AC 2.5.1 Section 8.5 refers. I cite these, only because they are jurisdictions in which I have flown. In these places, you do not fly 'in and out of controlled airspace'. Your SIDs and STARs are predicated upon you being able to achieve certain performance in order to comply, and to maintain the protection of that airspace. You are either inside and get the benefit of 'protection', or outside, and play the way the rest of us have to, controlled classes of airspace are there for the simple reason that high speed, heavy jets generally require such protection. I freely admit I know jack about how the US does it.

Originally Posted by SNS3Guppy

Those who would skirt airspace as closely as they can remind me somewhat of someone who might walk on the highway as close to the edge of the highway as possible. One might technically have stepped into traffic, but what if traffic drifts across the line, slightly? Doing the same thing in flight with altimetry systems that can be off slightly means that the analogy is a little more like walking along the highway blindfolded; you have no way of knowing exactly where the "edge" is. Give it a buffer. Stay on the sidewalk. Don't go near the edge. Playing near the edge is asking for trouble, whether it's performance, or airspace. I've spent much of my career in operations involving flight near the edge of performance, foreign airspace, and close to obstacles and terrain, and I'm paid in some of my employment to do just that. Are you? Then why go there?

Again, I suspect you have a reigonally-biassed view - In many parts of the world, being allowed to play in controlled airspace is unlikely at best; furthermore, in my part of the world the bottom of your controlled, protected areas is remarkably close to the ground - leaving us mere mortals quite a narrow zone in which to fly. When the controlled airspace is 1000ft AGL, and I have little hope of a clearance, you can bet your last dollar I'm going to have my fin right up against the bottom of it. You might equally well ask why the professionals need fly so close to the base, and the wild, uncontrolled chaos that reigns beyond..

[John R81]

A lot of gliders have a radio but do not have their FRTOL. So they're only allowed to operate on specific glider frequencies. That rules out getting a LARS. 31st Jan 2011 13:14


Surely that cannot be a reason pilots actually cite- "Better to risk a collision than to sit the exam for FRTOL"???? That seems to me to be as sensible as turning off Mode C (see all of above) - I know that I can, it's just that it would be so stupid at most times.

Still, we live in the real world and at present in the UK South the least visible of aircraft are the ones with no transponder and not on frequency. Seems from your post microlite and glider pilots simply accept that enhanced risk. LOOK OUT is the only option.

[IO540]

How often is the empty weight checked and by who?

It cannot be checked more often than at the Annual, so..... you remove the transponder for the Annual, possibly leaving behind just the antenna. The antenna can be installed (concealed) inside the hull if the hull is composite.

The empty weight is meaningless in safety terms because all the pilot has to do is eat a few more burgers and ... and GA pilots are hardly a health conscious lot.

[BackPacker]

Surely that cannot be a reason pilots actually cite- "Better to risk a collision than to sit the exam for FRTOL"????

I doubt there are a lot of gliders that reason this way. In fact, I doubt that there are a lot of glider pilots that know that there are ATSOCAS services available to them anyway. In general, I think their belief is that you only need the FRTOL if you want to pass through controlled airspace - which they rarely do.

Furthermore, the reality is that a lot of gliders *will* use the radio during their soaring flights. But they're on one of those dedicated glider frequencies and they will use it to keep each other updated on where the lift is, what altitude they're circling and so forth. Even if they wanted to (and were allowed to) talk to a LARS unit, they would need to switch to the LARS frequency and would be missing out important, possibly vital information from their fellow gliders. And no, a typical glider does not have the kit to monitor two frequencies at once.

All that, of course, apart from the distraction that this may cause. Which might be a reason for a glider pilot to switch off his radio altogether and rely on the Mk. 1 eyeball alone.

I'm not defending the glider community here. But I am dipping my toe into their waters (with a bit of luck and planning I should be able to get my GPL this summer) and I find that gliders have a completely different attitude towards radio, transponders and a few other things that power pilots simply take for granted.

[IO540]

I find that gliders have a completely different attitude towards radio, transponders and a few other things that power pilots simply take for granted.

I am sure that is true.

The problem is that a lot of power pilots also have a completely different attitude towards radio, transponders and a few other things that other power pilots simply take for granted

[pulse1]

Over the last two years I have asked several ATC units from OCAS to check our Mode C and the result has been OK. However, during a recent transit of Solent CTA at 3000', we were asked to switch off our transponder because they said it was reading 200' low. We later asked Bournemouth and Bristol Radars to check it and they said it was within limits. Calculations based on the displayed PA and the QNH confirm that it is slightly low but within limits.

As a Permit aircraft it doesn't usually go anywhere near expensive avionics facilities, how else can one verify the accuracy of Mode C?

[soaringhigh650]

Also, ever wondered why you need to state your altitude when you check-in on a new frequency? It's because the controller in the next sector needs to verify your mode-C reading.

So you'll find out pretty quickly if your mode-C is inaccurate!

[John R81]

BackPacker - always good to get a little insight into how other people think / reason.

Me, I would just carry 2 radios.
Come to think of it - I do have two radios in the cab. Overcautious. I should clearly live a little - take more radio risk!

[ShyTorque]

During departure, I'm busy getting cleaned up and configured for the enroute climb, and I don't have a really great view of other traffic, especially at our climb speeds which may be closer to 300 knots, even below 10,000 (minimum safe speed allows higher than 250). I may be on a vector, and I may pass in and out of controlled airspace during that climb.

SNS3Guppy,

Under what permission do you do that?

[lucaberta]

SNS3Guppy,

Under what permission do you do that?

that is a good question. Over here in Europe there are no strict regulations that force 250kts below 10,000', as far as I know (at least here in Italy), but in the USA no controller can issue deviation from an FAR which specifically says that every aircraft *must* be flying slower than 250kts below 10,000'.

I would be curious to know if you really keep the leading edge flaps out until 10,000' during climb when you're in the USA.

Ciao, Luca

[Rod1]

IO I did not see a smiley on this post, I hope that was an oversight!

“How often is the empty weight checked and by who?”

To get it installed requires paperwork, which includes the weight of the installation plus the old empty weight. It would also get checked after any accident or incident if the insurance or the CAA thought there was a problem.

”It cannot be checked more often than at the Annual, so..... you remove the transponder for the Annual, possibly leaving behind just the antenna. The antenna can be installed (concealed) inside the hull if the hull is composite.”

So, you are helpfully suggesting that people fly illegally and with a set-up, which would not work? Most of these machines will be composite – carbon fibre – and no you cannot hide the antenna in the fuselage cuz it wont work, would be illegal and no avionic shop would do it (we are talking factory built £80k+ machines)

”The empty weight is meaningless in safety terms because all the pilot has to do is eat a few more burgers and ... and GA pilots are hardly a health conscious lot.”

I and many others have tried to get the CAA to relax the rules to allow the installation to be excluded from the empty weight calculation. Many parts of the world have similar exceptions, but the CAA would not budge. Perhaps it would have been a better use of my time posting ridicules bits of advice on an aviation forum…

It is rules like the empty weight rule that make the VLA solution, which has no such silly rule, a better option.

Rod1

[Mark1234]

There's another thing that goes against gliders and transponders, multiple radios and the like - POWER. Specifically, everything must run off batteries, and when flights are frequently in the reigon of 5-10hrs, that can be a real issue.

I also rather doubt the practicality of working under ATSOCAS for gliders - they don't fly in straight lines, maintain altitude, speed, or anything like that for very long; if you were to tell someone every time you changed height/speed/direction, you'd never stop transmitting.. They also tend to want to look out the window, and enjoy flying, not play at airline pilots(!) Yes, I have a foot in both power and gliding camps..

@ShyTorque - In Aus it's pretty common to hear the 'heavies' ask for (and receive) "high speed climb", or "cancel speed restriction below 10,000" - As I understand it, the ATSU has the authority to allow as they see fit. Passing in and out of controlled airspace - er - goodness knows!

[ShyTorque]

Passing in and out of controlled airspace - er - goodness knows!

The "out of controlled airspace" is the part I was more interested in.

[John R81]

Mark

Messing around in a helicopter might give rise to as many changes in heading / height. Don't make so many radio calls that a battery operated hand-held would run out of juice.

Just the occasional call would let everyone on station have an idea where the glider is at that time.

[mm_flynn]

Originally Posted by lucaberta

that is a good question. Over here in Europe there are no strict regulations that force 250kts below 10,000', as far as I know (at least here in Italy), but in the USA no controller can issue deviation from an FAR which specifically says that every aircraft *must* be flying slower than 250kts below 10,000'.

I would be curious to know if you really keep the leading edge flaps out until 10,000' during climb when you're in the USA.

Ciao, Luca

Guppy's comments are directly relevant to the US where there is a hard 250 knot limit, UNLESS MINIMUM SAFE AIRSPEED dictates otherwise. There is then a list of aircraft to which this is likely to apply. Which I believe includes Guppy's 747. In the case of the FAA they do not define minimum safe airspeed as the minimum you can climb dirty, it is a clean climb configuration with sensible safety margin (can't seem to find the exact detail )

[SNS3Guppy]

However it is definitely possible to climb out and comply with the 250kt rule. Yes it may require flaps but it is perfectly possible and safe.

Economic; probably not, but since when has economy been the yardstick of "minimum safe airspeed"?

I'm not saying low level climbs at >250kt aren't done, just that it sounds like an airline accountant's interpretation of the rules.

No, it's not. We don't climb with gear and flaps out for a good reason; our climb performance, ability to meet departure procedure and climb gradient requirements, etc, is met in a clean configuration. We don't clean up because it's cheapest. We clean up because once we've met our immediate segment and obstacle climb gradient criteria, we clean up to meet our best rate criteria.

Flying a large airplane isn't the same as flying a Cessna 172 in this respect. Everything is numbers-driven. We have minimum performance criteria which requires certain operational practices, and it's part of the certification (and thus use) of the aircraft. We're also constrained by operational practices dictated through various policies, both governmental, industry, and standardized practices that have been evaluated to meet governmental and international guidelines.

Bear in mind that we operate everywhere but Antarctica, regularly. We're fully ICAO compliant, and we operate in a lot of places where terrain, noise abatement, airspace, and other requirements dictate that we stick to our climb profiles. After a standard departure, we clean up at 3,000', accelerate to V2 + 100, which is our minimum safe speed clean, and climb to 10,000, where we normally accelerate to 320 to 340 knots indicated for the initial climb.

Under what permission do you do that?

As a function of our IFR clearance, and our operations specifications issued to us by the government agency that oversees our operation...which includes operation in uncontrolled airspace. We don't ask what type of airspace we're in during a flight under IFR. We don't particularly care if it's class A, B, C, D, E, G, etc.

If you're asking about the permission for making a high speed climb, the requirement for 250 knots below 10,000, where applicable, applies only if the minimum safe speed of the aircraft is below 250 knots. We don't need permission. We "ask" as a courtesy, for a high speed climb, but also often simply inform ATC about our climb speed. ATC expects it. The one exception will be times when a departure procedure may require a slower speed and a configuration change may be delayed because until those requirements are met, the SID or DP establishes the speed. At that point, our primary concern is meeting climb gradients and crossing restrictions.

Accordingly, we also utilize turn procedures for engine-out situations on takeoff, at many locations, which are different than what are published for themasses. Our turn procedures are issued specifically to us, and may very well take us into uncontrolled airspace. If our turn procedure is a left turn to 180 degrees and our performance calculations give a level off altitude of 800', then we're climb to 800', leveling off, turning to 180 degrees,and advising ATC that we'll get back to them. ATC doesn't have this procedure; we advise them of what we're doing, make appropriate requests or statements, and handle the problem.

As another aside, part of our protocol when returning to land with certain malfunctions is to inhibit the TCAS RA functions by going to a TA mode only; we'll get traffic alerts, but not a resolution advisory. Our changes in performance or capability dictate that we don't presume to act on that traffic information. What that does is enables our TCAS to interface with other TCAS to require the other aircraft to come up with a resolution that doesn't need us to deviate. Such situations are specific, but tied to the idea where that we have performance limitations and procedures to abide, and before others in an uncontrolled situation elect to take full advantage of the extreme limits of their uncontrolled airspace (and let their PCAS do the traffic scan for them), they should be aware that three quarters of a million pounds of aluminum might be getting set to come through their windscreen. Plan accordingly.

Again, I suspect you have a reigonally-biassed view - In many parts of the world, being allowed to play in controlled airspace is unlikely at best; furthermore, in my part of the world the bottom of your controlled, protected areas is remarkably close to the ground - leaving us mere mortals quite a narrow zone in which to fly. When the controlled airspace is 1000ft AGL, and I have little hope of a clearance, you can bet your last dollar I'm going to have my fin right up against the bottom of it. You might equally well ask why the professionals need fly so close to the base, and the wild, uncontrolled chaos that reigns beyond..

I'm not sure how much of a regional bias I could possibly have. At the moment I'm typing from a hotel room in Korea. A little later I'll be in China. I was recently in the middle east, and Europe just before that. I operate about as globally as you can possibly get, so which region is it that influences me? Did you form an impression off what you thought you knew based on the little bit of information under my screen name? I've lived and flown and worked all over the world, and still do. Where my mail goes doesn't necessarily influence or color my "regional bias."

I've spent a lot of hours and years flying close to the surface in utility operations (ag, firefighting, animal survey, back country charter law enforcement, etc), much of it VFR. Much of that VFR flying, in fact transitions in and out of controlled and uncontrolled airspace without any regard to which is which, due to operational necessity. One thing I always do, however, is maintain a high awareness of where traffic conflicts can occur.

A buffer between the lower surface of a busy controlled terminal area and the upper limit of uncontrolled airspace is a potential conflict area. Giving it a buffer is in your best interest.

Sure, as a pedestrian you have the right of way over motor traffic. Betting your life on exercising that right of way against a road train or semi-truck is stupid at best, and extremely dangerous. Betting your uncontrolled rights in your spam can against the sanctity of the lower limits of the local controlled airspace, is likewise not a smart move on your part. Insisting on "sticking your fin" out of the uncontrolled tank may not be your wisest act.

How often is the empty weight checked and by who?

As often as one wants. The question is why check it more often than necessary, or more often than it's changed? Re-weighing is generally done at every annual inspection or every three years, depending on the aircraft and maintenance program under which it's operated.

By whom? Authorized personnel.

If equipment is removed, the weight and balance paperwork must be amended before the aircraft is released for service, again.

It cannot be checked more often than at the Annual, so..... you remove the transponder for the Annual, possibly leaving behind just the antenna. The antenna can be installed (concealed) inside the hull if the hull is composite.

Sure the weight can be checked more often than the annual. However, if a change is made in the weight and balance of the aircraft, the weight and balance paperwork must reflect this change, and should be amended by the person removing the equipment.

The empty weight is meaningless in safety terms because all the pilot has to do is eat a few more burgers and ... and GA pilots are hardly a health conscious lot.

The weight of the pilot is meaningless and irrelevant to the topic of empty weight, is it not? Pilot health consciousness has no bearing on empty weight of the airplane

[ShyTorque]

SNS3Guppy, The reason I asked was because under UK aviation law, you need a written permission to go above 250 kts in Class G airspace. I don't think ATC can give ad hoc permission on the day; Class G doesn't "belong" to ATC.

If you don't have it then don't be surprised if folk complain. I know one corporate operator who was warned off and threatened with further action for flying over 250kts. The evidence was his mode S transponder readout.

[Roffa]

ST,

SNS3Guppy, The reason I asked was because under UK aviation law, you need a written permission to go above 250 kts in Class G airspace. I don't think ATC can give ad hoc permission on the day; Class G doesn't "belong" to ATC.

Correct.

UK MATS Pt 1...

In Class E, F and G airspace, conflicting traffic may not be known to ATC and so it is necessary for all flights to make use of the 'see and avoid' principle. In order for this to operate effectively, controllers shall not authorise a relaxation of the airspace speed limit.

[mm_flynn]

There aren't likely to be any non-emergency, non- military heavily loaded heavies operating a climb profile in the UK outside controlled airspace, however, his point is similar to points UK ATCOs have previously made about why cutting a couple hundred feet into the bottom of LHRs departure airspace is a problem (which is not because aircraft are often scrapping the bottom, but sometimes they are - plus the obvious issue of 'it is against the rules')