Wake Turbulence - Trikes

[Guest davidh10]

I've pondered which forum to post this in, but the General Forum seems to be the best fit.

 

 

 

The objective is just to indicate the extent of wake turbulence created by trikes. We all study wake turbulence as part of BAK and I've seen posts here about whether or not experience of wake turbulence is gained during training. Certainly I think awareness of the vortices created by larger aircraft are well known.

 

 

 

The fact that some have said they would never execute a full 360 degree turn for fear of encountering their own wake has indicated to me that there may be little practical experience gained by students and new pilots.

 

 

 

I've previously flown into my own wake on two occasions, deliberately during lessons with instructor on board, however the effect was mild compared to this particular encounter, described below.

 

 

 

I had been flying in company with another trike; flying at varying relative levels and distances while taking photos. On the way back to the circuit for landing, I crossed behind the other trike at a distance of between one and two miles and at about the same relative height. We had both descended to overfly height for the aerodrome and were about three miles out. I was just in the process of counting off my transmit periods to activate the PAL when I encountered the other trike's wake turbulence. I have to say that priority number one (fly the aircraft) came sharply into focus as it pitched sharply down and to the left. I countered the apparent forces and it was over in a few seconds, with straight and level flight restored, however it is to-date the most significant attitude upset that I have encountered.

 

 

 

Trikes do create a surprising level of wake turbulence for the size and weight of the aircraft!

 

 

 

Hopefully this shared experience is of use to others :)

 

 

[Guest Crezzi]

With high AoA, very low aspect wing and relatively low speeds, trikes could almost have been designed to produce wake turbulence !

 

I'd certainly avoid doing steep level turns through 360deg as the plane is already close to (or at) the edge of the envelope and time taken to complete the manoeuvre means the vortex has very little time to dissipate.

 

Cheers

 

John

 

 

[Guest Andys@coffs]

Once at Wellington in SA I was with a group of trikes landing and through some bad decisions ended up too close to the trike in front and ran into wake turbulance about 40 ft off the ground. Despite full power and quick recovery movements I still touched one of my mains down on a sanddune to the side of the runway before starting the go around.... A few feet lower and I may well have stared in the back or the RAAus mag best case, or the back of the advertiser newspaper classifieds with my passenger worst case. When your taught not to get too close its for a very real reason!

 

Andy

 

 

[Spin]

Believe it or not even a paraglider creates a reasonable amount of wake turbulence. Strangely enough I always found that theirs was worse than a hang glider's when flying in company. The other trap for young players is the fact that the turbulence is slightly above the preceding glider - airline pilot mate of mine learnt the hard way when his glider turned to a bundle of washing just behind mine one day above the dunes:laugh:

 

 

[eastmeg2]

I'm having trouble believing that trikes have such a big wake turbulence 'foot print'......

Me too . . .

 

When doing circuit training all those years ago our CFI had that many of us in circuit that 500m separation was about the most we could achieve and while there was some noticeable wake turbulence it was easily manageable.

 

I personally wouldn't fly closer than about 300m behind another trike at the same altitude or that is less than 100ft higher.

 

Years ago I have had another trike veer in front of me less than 100m in front and it was all I could do to dive my trike out of his wake. I was about 1,500ft AGL at the time and wouldn't have wanted to be close to the ground when that happened.

 

 

[alf jessup]

A friend of mine was following me one day in his trike on a trip across to Mt Beauty, as i often couldn't see him as he wanders around much to my displeasure i asked his position and he promptly informed me he was directly behind me about 500 meters and about 100 ft below my level.

 

I kindly advised him that it was not a good place to be and i would rather have him in a position where i could see him.

 

He replied "i'm fine and i'm happy following you".

 

5 or so minutes later i just happened to look out and down to my port side only to see old mate in a about a 60 odd degree bank 1000 odd ft below heading towards the west were we were supposed to be tracking due north.

 

Being on the chat channel i transmitted "XXXX old mate why the hell you heading west and i'm heading north turn back to the north you dill".

 

Not a word was spoken by old mate and he came back to the north and sat off my port side the remainder of the way.

 

Upon landing and after shutting down and securing the trikes old mate came over almost white (he was born in India) and promply informed me how bad the turbulence was and how one minute he was following me and the next he was in a 90 degree bank and diving. I said to him what turbulence??? it was as smooth as silk and i happened to be hands off enjoying the view.

 

It then dawned on me that he flew into my wing tip vorcities and I now knew the reason why he hadnt replied when i questioned him about his westerly heading as he wasnt game to let his grip go of the control bar to the ptt.

 

My reply was "na was as smooth as silk but you flew into one of the tornado's coming off my wing tip and that is why i told you not to be directly behind me and below.

 

I guess I could have explained it to him prior to the event happening but i just presumed he would have known.

 

One thing was learnt that day was old mate now NEVER follows behind and slightly below now if he is behind he is about 300 ft higher.

 

Was funny at the time after we landed and i found out but it could have been really bad.

 

Even now i give all aircraft landing ahead of me trikes and GA plenty of separation.

 

Cheers

 

Alf

 

 

[Guest Andys@coffs]

I'm not saying that Trikes generate more WT than anything else (I havent a clue if they do or dont) What I am saying is that they react very badly when they fly into trike generated WT. It could be that if they fly into WT generated by something a bit bigger than the trike that the result are even more spectacular.

 

However the only things that Trikes are likely to find themselves catching up to is another trike so perhaps the number of experiences of flying into a kingair or 747 WT is therefore limited in a trike...or they havent yet found all the bits.

 

I think that the reason that WT is severe is the light wing loading. Any T in a trike can be uncomfortable when in another aircraft at the same time and place you'd say what T?

 

Andy

 

 

[Tracktop]

Ok here are some thoughts why turbulence in a trike can be uncomfortable.

 

Feel free to correct me as I am just thinking out loud

 

The trike wing has very low inertia as most of the weight is in the base, ~2m below the center of wing balance and free to rotate independantly.

 

This means the wing is fairly free to follow the Turb ( rock from side to side, up down) with the pod just swinging freely below and essentially just tethering the wing (no pilot input).

 

In a rigid 3 axis the fixed weight tends to dampen the Turb effect as any effect must move the hole mass as one.

 

In a trike you still feel what the wing is doing through the bar so the quick wing movement is very noticeable on the end of a 1.5m leaver.

 

Being ~2m from the rotation axis is a bit different than sitting at the center of the rotation axis

 

My understanding is the trike can handle the turbulence ( obviously within limits) , its the pilot that has the problem???? and maybe rightly so ???

 

and that's without getting too technical.

 

I guess we are using similar HP to push through the air but at a slower resulting speed so more drag and thus turb ?

 

Though we still seem to use similar fuel to travel the same distance so 3 axis faster speed / same HP used should = similar turb ????

 

Coarse theory based on cause and effect being equal ??

 

Thoughts??

 

 

[pudestcon]

G'day David,

 

I'm not meaning to disbelieve you but is it true you were "at a distance of between one and two miles" behind? I find it hard to comprehend that turbulence would still be strong enough to have much effect. I don't fly trikes but it has certainly raised my awareness of the phenomenon. I have tried on a number of occasions to fly through (in a Thruster) my own wake during a steep turn but have had no sensations whatsoever.

 

Pud

 

 

[Tracktop]

Very easy to do in a trike Pud and it is very noticeable though not usually outside normal flight conditions.

 

The more you go round the worse it gets too

 

Some of it may be the shock effect to, as it comes unexpected if general conditions are smooth.

 

It can catch you out as others have described if you are relaxed ( due to nice conditions ) and not ready to react quickly.

 

Have to get a plug in here - hit by WT and respond in your 3 axis reflex action ( low hrs trike hi hr 3 axis ) and things may not be nice at all.

 

 

[pudestcon]

Trikes haven't 'done it' for me in the past but what with all the discussions on trikes here I must confess my interest has grown. I just might have to pay GordonM a visit out at White Gum Farm and give 'em a try. The sensation of 'riding a motorbike at 1000 feet' certainly appeals.

 

Pud

 

 

[Guest Crezzi]

Ok here are some thoughts why turbulence in a trike can be uncomfortable.Feel free to correct me as I am just thinking out loud

The trike wing has very low inertia as most of the weight is in the base, ~2m below the center of wing balance and free to rotate independantly.

 

This means the wing is fairly free to follow the Turb ( rock from side to side, up down) with the pod just swinging freely below and essentially just tethering the wing (no pilot input).

 

In a rigid 3 axis the fixed weight tends to dampen the Turb effect as any effect must move the hole mass as one.

 

In a trike you still feel what the wing is doing through the bar so the quick wing movement is very noticeable on the end of a 1.5m leaver.

 

Being ~2m from the rotation axis is a bit different than sitting at the center of the rotation axis

 

My understanding is the trike can handle the turbulence ( obviously within limits) , its the pilot that has the problem???? and maybe rightly so ???

 

and that's without getting too technical.

 

I guess we are using similar HP to push through the air but at a slower resulting speed so more drag and thus turb ?

 

Though we still seem to use similar fuel to travel the same distance so 3 axis faster speed / same HP used should = similar turb ????

 

Coarse theory based on cause and effect being equal ??

 

Thoughts??

With low airspeed & high AoA there's lots of induced drag hence wake turbulence. I don't know if a trike produces more wake than a 3-axis of similar weight and aspect ratio (E.g Thruster or Drifter ?) flying at the same speed. My personal experience suggests that it does but I'm not an aerodynamicist ! Possibly the combination of washout and sweepback increases the crossflow.

 

I have heard it argued (by pilots very experienced on both) that trikes are more comfortable in turbulence than a 3-axis of similar wing loading precisely because of what you describe Ray - the wing is deflected but the pod (& occupants) less so. The correction takes a bit more of an effort in a trike though !

 

Cheers

 

John

 

PS good to see you haven't been convinced by the control reversal argument

 

 

[farri]

I`m not a Trike pilot,just asking.

 

Wouldn`t all that mass bellow the wing, create heaps of turbulence,bossibly more than the wing itself ??????

 

I can tell you that some Trikes certainly can catch up to other aircraft,a couple of local guys have Trikes powered by Rotax 912 and I`ve got no chance of catching them in my 503 Drifter,they leave me behind by a long way and I`ll be doing 50/55 indicated,couldn`t believe it when I first tried it,I`ve got no chance of catching them..

 

Now for those who do 100/110, I know 50/55 is slow but the country is so great here in the north that it gives time to realy take it in.

 

Frank

 

 

[Guest davidh10]

G'day David,I'm not meaning to disbelieve you but is it true you were "at a distance of between one and two miles" behind? I find it hard to comprehend that turbulence would still be strong enough to have much effect. I don't fly trikes but it has certainly raised my awareness of the phenomenon. I have tried on a number of occasions to fly through (in a Thruster) my own wake during a steep turn but have had no sensations whatsoever.

 

Pud

No problem Pud. There's other disbelievers too, and that's fine. I posted to be useful information based solely on my actual experience. Others can make of it what they will. Certainly there is a range of experiences and opinions that have been expressed and it is a good discussion.:)

 

It is possible that I misjudged the distance and was a little closer than stated, however I checked the distances as perceived on Google Earth, before posting, so I'm reasonably sure it was less than two miles but wasn't less than one mile. Given that, the distance measurement is subjective.

 

Here is an excerpt from the out-of-band response from another trike pilot who was observed recently to have approached the likely position of the wake of another trike. I had sent him an email relating my experience and asking if he was aware that he had been close to the wake of the specific trike. As he is not a member here and it was a private email, I've edited it to remove any means of identification.

 

"Yes, I did experience an unexpected movement of the trike's wing.... I did not contribute [sic] it to wake turbulence at the time as I was quite far behind, but following your experience it may well have been wake turbulence - my wing also tried to turn sharply left and I struggled to stop it. Fortunately the forces were only evident for a brief moment. I suppose the wash out of the back of the trike wings is quite significant, something to keep in the back of the mind in future."

 

 

[Guest davidh10]

I`m not a Trike pilot,just asking.Wouldn`t all that mass bellow the wing, create heaps of turbulence,bossibly more than the wing itself ??????

 

I can tell you that some Trikes certainly can catch up to other aircraft,a couple of local guys have Trikes powered by Rotax 912 and I`ve got no chance of catching them in my 503 Drifter,they leave me behind by a long way and I`ll be doing 50/55 indicated,couldn`t believe it when I first tried it,I`ve got no chance of catching them..

 

Now for those who do 100/110, I know 50/55 is slow but the country is so great here in the north that it gives time to realy take it in.

 

Frank

Probably not just the mass below the wing, but also, with a pusher prop, anyone behind is subjected directly to the rotating cone of air behind the prop, disturbed only by the wing vortices.

 

I was at 60kn IAS at the time and the trike ahead was an SST wing, so was probably doing 70kn IAS at the time. I know the distance between us was increasing.

 

 

[Guest davidh10]

Trikes haven't 'done it' for me in the past but what with all the discussions on trikes here I must confess my interest has grown. I just might have to pay GordonM a visit out at White Gum Farm and give 'em a try. The sensation of 'riding a motorbike at 1000 feet' certainly appeals.Pud

Yep. Give 'em a go. They are great, particularly for photography, as there's no window between the lens and the subject. You just need to rug up a bit with in the air temperatures between 2 and 8 degrees at present. Here's a link to whet your appetite :big_grin: