Does anyone know what the effect - if any - of a slightly bent VOR antenna is? Does it have any effect on the accuracy of the VOR or ILS?
of a slightly bent
Depends on how much "slightly bent" it is! The VOR antenna is a dipole antenna, and if it is sufficiently bent to become a monopole antenna, it will lose 1/2 of it's gain. Which means that the useful reception range will be only one half. Probably still sufficient to fly an ILS, but maybe not for longer range VOR navigation. But who does that in the year 2013 anyway?
Without having seen your antenna, I would guess that for practical purposes it should be OK.
Can't you just bend it back? Sooner or later you'll have to replace it anyway and if it breaks in the process, then it will be rather sooner than later.
Does it have any effect on the accuracy of the VOR or ILS?
ADF uses a direction-sensitive loop antenna to determinate the direction to the beacon. Modifying the ADF antenna would directly impact the accuracy of the reading.
However, with VOR or ILS the antenna is not used to sense direction. Therefore, the accuracy of the reading will be unaffected, but as "what next" said: The range might be negatively impacted.
Thanks. yes I could bend it back but politics of the group etc ......
Thanks for the quick responses.
The antennae tend to be a metal rod in a fibreglass sheath, and the rod can snap inside the sheath. The rod especially tends to snap near its base. So if you get a bent one, it should not be bent back.
You can fly around with such a fault for ages, and most "radio checks" won't find anything wrong because they are done by a man standing next to the plane holding the test set.
AFAIK there are just two ways to spot a broken NAV (VOR or LOC) antenna:
by walking around the plane at different compass positions and reducing the signal level at each position until the flag drops, or
by doing an attenuation check, which I think needs a connection into the coax cable
I know of only one man who does the above...
How did it get bent in the first place? It's normally high up on the tail.
Peter, it got bent by the use of the external covers which the group insist on using in the hangar - FULL external Cambrai covers when in the hangar! It has caused many, many discussions, arguments, disagreements, arguments about the group's rules, the group's voting mechanism etc. etc.
I've sent them all plenty of info about the risk of condensation when being hangared with full covers, I've sent them photos of condensation on the top side of the wings, underneath the wings, the paintwork is being scratched, we need a repaint in the next year or two due to the corrosion over the aircraft. There are a minority who insist that we use them (a) because we bought them (when we were outside) and therefore it would be "silly" not to use them (b) thats what we've always done (c) the damage caused by dust is far more damaging than the damage from corrosion (d) the motives behind a change to lightweight dust sheets are because we (the majority) can't be bothered etc. etc. etc. I won't go into a full rant but I'm getting there - again! I've spoken to Piper who don't recommend them, have a Sqn Ldr friend with a first in Aeronautical Engineering send a detailed explanation of the condensation issue etc. AARGHH!
Yeah, not a simple issue 
I use a Bruce's Custom cover all the time (in the UK, mainly to stop passers-by casing the joint during the rare times it is outside the hangar where I am based) and abroad in hot climates to stop the cockpit getting really hot. But it must never touch the ground otherwise it picks up grit and scratches the windows. If it ever falls down on the ground I have it laundered.
Re condensation, by far the best solution is to keep a 0.5kg bag (or two) of silica gel in the cockpit, and change it weekly. The used bags can be baked at +120C overnight, originally cost only £5, and can be recycled many times. I get them from here; make sure you get cloth bags and not paper bags which cannot be baked. This keeps the cockpit totally fresh as new, after 11 years. I have measured a 10% drop in RH, which totally stops any condensation. I used to get condensation on the instruments, on a cold morning, before I started doing this.
Hi Peter, Where do you get your cover cleaned Robert
Believe it or not, a laundry bought a hangar here at Shoreham!
I took it there, £15, but they washed it hot and it shrunk ~5%. A lesson for next time. Would have never happened to a girl 
But it was done within hours and came out spotless.
