C172 contrails

[Gerard123]

Has anyone ever seen or have photos of a C172 or similar with contrails? I thought I saw some a few weeks ago but couldn't be certain. Does anyone know what conditions would required to get contrails on such a light plane?

[ShyTorque]

Contrails? Knackered piston rings, more like!

[Sensible]

Or maybe the pilot was aspiring to be a "Red Arrows" display pilot;)

Contrails are made up of minute ice crystals caused by the freezing of water vapour produced on combustion of a hydrocarbon (avgas). The air would need to be exceedingly cold in order to freeze the water vapour created by combustion. The products of combustion of avgas being in the most part carbon dioxide and water vapour. Realistically the aircraft would need to be above 25,000 ft which is well above the service ceiling of most 172's

[GroundBound]

Perhaps you are thinking of wing-tip vortices?

In very humid conditions, the drop in pressure over the wings can cause the moisture in the air to condense which then forms a short vapour trail, usually at the wing tip. (I stand to be corrected on this, :) )

However, this is rarely produced in light aircraft which are relativley slow moving.

GB.

[Sensible]

Thinking about it, even if conditions were right, I don't think that a 172 would produce visible contrails because the exhaust volume is just insufficient. Not sure that a 172 would produce a visible wing tip vortice either. Bit like looking for a urine trail from an ant!

I think the first answer about a knackered engine or a fuel additive to be the most likely reason and it would be visible smoke not water vapour!

[Genghis the Engineer]

It's entirely possible if flying at conditions of high humidity and temperature around the dewpoint for the pressure drop within the wingtip trailing vortices to cause visible fine condensation to drop out. If you want to call this a contrail, be my guest!

I'd struggle to find the reference, but recall reading somewhere that this was a problem suffered during WW2 by the photo-reconnaisance Spitfires, etc. over Germany - if you weren't careful to stay out of the band of temperature / altitude / humidity where this could occur you were at risk of broadcasting your existence to half of Germany.

G

[airborne_artist]

'd struggle to find the reference, but recall reading somewhere that this was a problem suffered during WW2 by the photo-reconnaisance Spitfires, etc. over Germany - if you weren't careful to stay out of the band of temperature / altitude / humidity where this could occur you were at risk of broadcasting your existence to half of Germany.

The Fortresses also left contrails under similar conditions.

[Cutoff]

Many Piston Aircraft left contrails in the war, this was at very high altitudes however. And yes the recon aircraft had to be very careful of this, in fact so did some bomber missions, small numbers of aircraft doing precise bombing runs to very sensitive targets. They sometimes used chase aircraft and scrubbed the mission if contrails were forming.

I have seen wingtip vortices off light aircraft in very humid conditions though and I, as other have suggested too, suspect that it is these that are the subject of the topic.

[ShyTorque]

:uhoh:

Just think CHEMTRAILS.......... :E

[Final 3 Greens]

Aw man, I'm just too spaced out and relaxed to think at all, after that 172 tanker sprayed us this morning :D

[Shaggy Sheep Driver]

Wingtip vortices are usually only visible when humidity is high AND wing loading is high. Vortices are therefore most commonly seen from commercial airliners during the landing approach, and at rotation on take off, when angle of attack is high. On more heavily wing-loaded fighters, vortices can be produced in turns as well (and I've seen the whole top surface of Tristar's wings disappear in vapour as it commenced a post-take off low speed turn).

Our Yak 52 sometimes produced vortices off the prop tips, but I very much doubt a 172 would ever produce vortices unless being manouvered quite vigourosly on a very humid day - but not in straight and level flight.

SSD

[Brooklands]

I haven't seen anything like this on a 172.

A few years ago I was visiting an airfield, and saw and aircraft (cub or robin, can't remember the type for certain) flying the downwind leg with, apparantly a thin trail of smoke or oil behind it. I was on the point of going to raise the alarm, when I realised that it was a glider tug, and what I could see was the tow rope.

Brooklands

[jabberwok]

Vortices aren't just confined to wingtips - you get some pretty spectacular ones from flaps too.

[Shaggy Sheep Driver]

Vortices aren't just confined to wingtips - you get some pretty spectacular ones from flaps too.

And prop tips, cockpits, and all sorts of other places if conditions are right. And jet intakes when full power is applied for takeoff and the intake pressure drops as the engine sucks air :O


SSD

[ShyTorque]

A true contrail consists of ice particles, so they only persist well above the zero degree isotherm. The trail is generated from aircraft exhausts, where water vapour is introduced to the atmosphere. It then cools / condenses very rapidly into ice crystals which reflect light. There is always a gap between the exhaust outlet and the beginning of the contrail, this is where the water vapour is not yet cooled enough to condense.

We used to be given the contrail level in our morning met brief.

I was once told a story by a Group Captain (anyone remmber Phil Langrill?) who told me he went up on an early morning handling check airtest in a Hunter from RAF Valley in a beautifully clear sky. Having climbed on a heading, he levelled off for a short time on the same heading. He then carried out a 180 degree turn, followed by another minute or so straight and level. He then flew a steep turn one way, briefly rolled out, then did another steep 360 in the opposite direction.

Airtest complete, he descended and returned to Valley. Very shortly afterwards, following local complaints about a huge picture of a penis and testicles in the sky, they had to fly a four ship formation to go up and cross it out!!

[Gerard123]

Oh dear, sorry guys I meant vortices.

The ones I think I saw were at night (just after dusk) off the flaps on finals. I had 30 degrees. I'm really keen to see if I can make them appear on a 172 again. What sort of conditions (numbers) should I look out for to get the highest chance of producing these things? Obviously I want to do it safely, someone said something about manuevering but lets face it the 172 is a straight and level bird.:ok:

[Onan the Clumsy]

You're all wrong and there's a very simple solution...


...he left the gas caps off :ooh: :uhoh: :{

[jabberwok]

What sort of conditions (numbers) should I look out for to get the highest chance of producing these things?

About ten seconds before the airfield fogs out.. ;)

SSD is right - Temp and Dew Point as close as possible. You need really high humidity.

[Gerard123]

Ok, thanks I'll have keep a look out for some misty days :ok:

PS Onan don't be stupid I always check the....um whats that... UH OH:mad: mayday mayday !!!;)

[javelin]

Years ago, we were parachuting at Leeds Bradford, we used a Cessna 206, G-ATCE and it was running in at 12,000, a little unusual then. Several of us noticed a contrail starting about half an aeroplanes length behind it, it didn't last long, but it was definitely there.

[Kolibear]

A couple of weeks back, flying on a damp day, I was convinced that I could see a small, thin trail of vapour coming off of the outboard corner of the flaps. The flaps are permanently drooped to 6degrees so there is a sharp point to propogate avortex. It was only visible on the down-sun side of the aircraft, the other side being too bright to see if there was a trail coming off of the other flap.

I can only assume that as Genghis said earlier, the corect conditions had been met for small vortices to apear.