AnthonyQ wrote:
Does anyone have an opinion on the single altimeter
In the Netherlands it is quote common to have a single altimeter (VFR and IFR)
Bathman wrote:
Then if I have a com box failure i would at least be legal to get home or get to maintenance using com 2.
A few weeks ago I lost my KX155A in the Nav II-position in smoke. I was really happy to have the KX165A working in the Nav I-position.
Peter wrote:
Also, Vs of an F16 or similar is about 160kt depending on config.So I don’t think they would do an interception on a C172 with a jet.
A helicopter is much more likely, unless there is a particular hurry… During the UK 2012 Olympics they used helicopter patrols, with snipers in them.
They can’t land slowly, but they can fly slowly. I have heard of intercepts of SEPs with jets. AFAIK they would scramble a jet even after a helicopter. Helicopters would have to be deployed all over the place otherwise interception would take ages, they don’t have the performance to intercept anything other than slowish SEPs/ MEPs and I doubt they’re cheap to run. IIRC they were used to guard specific areas like during a NATO Summit where they could indeed be used to intercept and escort aircraft (small area makes the lower speed less of a factor).
I imagine that in the case you mentioned they were intended against ground targets. But they could obviously send it to intercept if they have it in the area.
Agree. A second AI is more useful. Which does not mean it ought to be mandatory!
Peter wrote:
Two altimeters… well the 2nd one can be a “cheap” one
The problem with the idea of two altimeters is (especially in a light single) the opportunity cost, not the money cost. You don’t have space in the panel to spare. I would far rather have a second attitude indicator than a second altimeter. Altimeters seldom fail (and if they do, it’s usually a problem with the static system – and good luck getting an independent static system put in your EASA CofA plane for the second altimeter). However, attitude indicators, especially mechanical ones reliant on the vacuum pump fail quite a bit more frequently. But once your last remaining instrument hole is taken up by that extra altimeter that’s not going to give you all that much redundancy anyway, then you just don’t have the option for a backup AI.
Peter wrote:
So I don’t think they would do an interception on a C172 with a jet.
Then you should refresh the procedures for interception, mandatory stuff I believe 
I think the thing has always been about redundancy. Today transponders are mandatory for instance, which is not a full parallel redundancy, but enough backup in case radio or alt is lost. Seems to me there are more practical reasons to have two radios, and a radio isn’t that expensive compared with a €500k IFR machine.
Airborne_Again wrote:
This looks to me like another case of security theater.
They’re not necessarily doing it because they think you might attack someone. They’re sometimes doing it to make you visible to ATC.
So safety theatre, perhaps
what_next wrote:
Don’t know who paid for that.
Well, you did.
I quite like the idea one one radio and one altimeter
Then if I have a com box failure i would at least be legal to get home or get to maintenance using com 2.
Nothing worse then being grounded at some regional interglacial spaceport that has 3 movements a day but your avionics man not allowed to bring a volt meter to the aircraft to fixit. Or a replacement nav/com for that matter.
No reason why one decent GPS/COM/ILS box with terrain, one transponder, electric standby attitude, six pack or glass should meet most safety standards. As Europe doesn’t allow overlays we still get accidents where one of the causes is substituting GPS for DME without reading the plate. With overlay this should not occur as it is taken care of in the GPS approach database.
The weakest link after the pilot is the electric system, so having triple com or NAV redundancy without dual electrics and split buses is a spurious safety blanket, unless your avionics are mid seventies vintage.
