SR22 GAP Seal

Hello everyone. I’m new to the forum so if I don’t follow forum protocols properly just let me know.

I have a question that I’ve not been able to get a clear response relative to the GAP Seals on the SR22.

During my walk around yesterday I found the Right Aileron GAP Seal was missing. This item in the POH is identified as Security. I could not find any where in the POH that I can fly the plane with this item missing so I cancelled the flight.

Can some tell me definitively if the SR22 can be flow with one ore both Gap Seals missing.

I seem to remember that during the Cirrus certification there was a fatal crash with the lead test pilot and the Gap seal may have been a factor.

Thanks in advance.

Good memory!

The gap seal crash was a result of a previous version of a gap seal deflecting during wing flexing while manoevering, which then jammed the aileron in a deflected position.

The smaller rounded gap seal cannot do this (maybe if it actually becomes detached in flight but I doubt it).

I don’t know if it is a legally required item for flight but I would assume it is.

Certainly I personally would not fly the airplane with asymetrical wing conditions in case you found yourself in a bad situation that this might be the final nail in the coffin in a (now) unrecoverable loss of control situation.

If it were really critical that I fly the plane somewhere I would first remove the other gap seal.

In reply to:


Can some tell me definitively if the SR22 can be flow with one ore both Gap Seals missing.


It cannot. The stall characteristic may be dramatically affected by the asymmetric configuration.

I have flown a Cirrus for about 15 hours with one seal missing with out any noticable problems, I talked to an engineer at Cirrus who told me to at least remove the other seal if one is lost. I also don’t see how this is an airworthy issue due to the fact that it’s attached to the aircraft with double tape. Any thoughts on this???

Thank you all for responding with you comments. I’ve been out of town for a few days so I’ve not had a chance to read all your comments. However, I would like to share with the forum a response I received from Cirrus Design below relative to the GAP Seal. I looks like the Plane can be flown without the Seals.

Thanks again for your responses

Insert********
-----Original Message-----
From: Peterson, Rich On Behalf Of Field Service
Sent: Monday, February 19, 2007 3:43 PM
To: Cirrus Aircraft Information
Subject: RE: Cirrus Website Request Form

According to Cirrus Engineering the aileron gap seal is not required and will not make the flight control surfaces ineffective, although the performance is better with the gap seals on. Thank You Rich

-----Original Message-----
From: Larson-Hagen, Brianna On Behalf Of Cirrus Aircraft Information
Sent: Monday, February 19, 2007 8:25 AM
To: Field Service
Subject: FW: Cirrus Website Request Form

Hi,

Can someone answer Don’s question?

Thank you!!


In reply to:


Good memory!
The gap seal crash was a result of a previous version of a gap seal deflecting during wing flexing while manoevering, which then jammed the aileron in a deflected position.


I doubt the SR22’s gap seal was directly involved in the crash of the first SR20, if for no other reason that SR20s don’t have them and it was a pre-SR22 SR20 that was involved. But I do think it is reated the the size of the gap.

In reply to:


The smaller rounded gap seal cannot do this (maybe if it actually becomes detached in flight but I doubt it).
I don’t know if it is a legally required item for flight but I would assume it is.
Certainly I personally would not fly the airplane with asymetrical wing conditions in case you found yourself in a bad situation that this might be the final nail in the coffin in a (now) unrecoverable loss of control situation.


I am pretty sure that it is a “NoGo” item. I have landed and found that one was missing. Yes, it did depart in flight! I noticed no difference in flight, but I never approached any extreme flight regimes. Having said this, using my lucky experience as any sort of guide would not be advisable.

In reply to:


If it were really critical that I fly the plane somewhere I would first remove the other gap seal.


With all due respect to Rob and his usually unimpeachable advice, please don’t follow this suggestion. I don’t know if it is a balance issue or a control issue. I suspect that it is the latter and related to airflow. I can’t belive that having two bad wings is better than one. Either way, please don’t fly with one or two missing until you clear it with a Cirrus knowledgeable A&P.

In reply to:


I doubt the SR22’s gap seal was directly involved in the crash of the first SR20, if for no other reason that SR20s don’t have them and it was a pre-SR22 SR20 that was involved. But I do think it is reated the the size of the gap.


The alternative Cirrus first used to provide gap seal functionality was involved in the fatal crash of that 20 - but Marty is right not directly. But the good news for us is that area was redesigned and now cannot happen. And in fact the crash plane had no gap seal remotely like we have - so you’re 1/2 right Marty [;)] Its really more accurate to say the original plane had a different type of seal - but that seal did cause the crash and our newer style gap seals had nothing to do with it .
The original plane had an overlap of composite material that went rearwards over the aileron - that was in effect a permanent gap seal. It also had a aileron that was open on the front. The wing flexed in some maneuvering (not sure anyone knows these details) and the open aileron lip was able to get on top of the composite gap seal causing full deflection of that aileron.
To insure this never happened again, Cirrus chopped back the composite material and closed the front of the aileron. They then installed the gap seal we currently have to get back any speed loss.
edited for clarity

In reply to:


Its really more accurate to say the original plane had a different type of seal - but that seal did cause the crash.


So then you absolutely agree with my comment that the current SR22 gap seal did not have anything directly to do with the accident other than to say its design may have been a result (not cause) of that accident?

This is one of those things where I would consider what is “The Most Conservative Action”.
Flying with one gap seal missing probably won’t cause major problems. And it’s hard to imagine a flimsy piece of plastic causing a huge problem if it wasn’t there.

But the seals are there for a reason. I can imagine a stall situation (even on landing) where the side without the seal could stall first. And all the control problems that could entail.

Likely? Maybe not. Possible? I’d say so.

Just my .02.

In reply to:


I have flown a Cirrus for about 15 hours with one seal missing with out any noticable problems, I talked to an engineer at Cirrus who told me to at least remove the other seal if one is lost. I also don’t see how this is an airworthy issue due to the fact that it’s attached to the aircraft with double tape. Any thoughts on this???


Please don’t do a stall series while flying in that asymmetric condition. It may be just fine within the normal flight envelope as you experienced, but that does not mean it will not bite you at an inopportune time.

When the aircraft are produced, a test pilot flys each one and goes through a stall series, which can result in small repositioning of the stall strips on the wing to ensure symmetric stall characteristics. By flying with only one aileron seal, you negate that preparation.

In reply to:


Thank you all for responding with you comments. I’ve been out of town for a few days so I’ve not had a chance to read all your comments. However, I would like to share with the forum a response I received from Cirrus Design below relative to the GAP Seal. I looks like the Plane can be flown without the Seals.
Thanks again for your responses
Insert********
-----Original Message-----
From: Peterson, Rich On Behalf Of Field Service
Sent: Monday, February 19, 2007 3:43 PM
To: Cirrus Aircraft Information
Subject: RE: Cirrus Website Request Form
According to Cirrus Engineering the aileron gap seal is not required and will not make the flight control surfaces ineffective, although the performance is better with the gap seals on. Thank You Rich
-----Original Message-----
From: Larson-Hagen, Brianna On Behalf Of Cirrus Aircraft Information
Sent: Monday, February 19, 2007 8:25 AM
To: Field Service
Subject: FW: Cirrus Website Request Form
Hi,
Can someone answer Don’s question?
Thank you!!



That makes it clear you can fly without both seals. I wouldn’t fly with only one missing.

I’ve listened and bit my tongue for a while whilst the uninformed pontification goes on as if it were gospel and the issue continues to get further confused. I even let the shot at not following in the line of my dangerous attitude go by.

Frankly, I didn’t want to engage in this argument… you know the Special Olympics and arguing on the internet and all!

However now that Cirrus has delivered it’s Holy Blessing and set the record straight I will elaborate on the role of aileron gap seals on the Cirrus.

(I was heavily involved with my late friend Jim Bradshaw when we as Knots 2 U developed aileron and flap gap seals on the Comanche line.)

95% of a gap seal’s benefit is for increased cruise speed. The high pressure air beneath the wing literally creates a vertical curtain of high pressure air chordwise along the upper surface of the wing at the leading edge of the aileron -or flap.

Visualize one of those high velocity air curtains they use at the doors to air conditioned stores and industrial freezers. Now imagine that blowing UP from that gap on your wing. It is aerodynamically like maybe a two inch metal fence. ROUGH numbers to get an idea of the flat plate area of 72" x 2" per aileron (double that because there are two ailerons) you MIGHT have a factor of TWO square feet of additional frontal area adding drag to cruise flight!

Now despite the dire warnings… the removal of the aileron gap seals will actually IMPROVE low speed handling!

Why?

Because at high angles of attack the downward deflected aileron is actually REALLY at a high angle of attack and is pretty close to the stall if not already there. The downward deflection of the aileron at or near the WING stall speed causes that aileron to become stalled long before the wing stalls. At that point is is not much of a wing, it may as well be a sheet of plywood or your kid’s arm “flying” out the car window driving down the highway. It is only providing flat plate lift from the bottom and NOTHING from the upper aileron surface.

BUT… if you remove the aileron gap seal at low airspeeds/high angle of attack, you will have a nice flow of air between the trailing edge of the wing and the forward curve of the leading edge of the aileron! This airflow is relatively slow now so it will allow the aileron to continue to “fly” a little longer and deeper towards the wing stall.

Kind of like a crude Fowler flap or a leading edge slat on the heavy iron!

So, the aileron gap seals improve cruise performance and MAY reduce aileron effectiveness near the wing stall.

This is why FLAP gap seals aren’t generally used, The effect of the flaps in cruise is insignificant when balanced against the decrease in effectiveness in lowering stall/landing speeds!

All of this was borne out in the STC process flight testing that I was involved in many years ago.

In fact, Roy LoPresti never did offer a flap gap seal for the exact reasons I just explained.

We did because post 1961 Comanche’s had full fowler flaps and the flap gap seals really didn’t do anything detrimental to the low speed handling. Cruise performance improvements were less than 1 knot @ 150 KIAS and were not repeatable so they are pretty much ineffective. Jim figures adding an extra couple of strip of aluminium for $20 would help justify the $1000 cost.

So you’d get FOUR strips instead of two!!!

In summary, IF I had have lost a gap seal prior to the Cirrus Decaration I would not have flown (hey I’m not a test pilot!) unless it was an EMERGENCY… like a double date with Rick supplying the girls! And then I would have certainly removed the other seal because asymetrical ANYTHING that far out on the wing can’t be a good thing if I happen to find myself DEEP into an aerodynamic coner… no matter how insignificant!

Hope this helps.

robapens,

Thank you for a very informative analysis of the Gap Seal question. I find it interesting that even given your experience with this issues you would choose not to fly the plane without the gap seal. As I mentioned I choose not to fly with the missing Gap seal and my checkout instructor also agreed but he did face some questions as to why the flight was not taken. Even with the response from Cirrus Design I would have made a no go of the flight. My reason is that from my perspective the Cirrus is still too new and bugs and anomalies are still being worked. I will contradict myself by saying that I think it is the safest single on the market. In my opinion. Thanks again for your response.

In reply to:


I find it interesting that even given your experience with this issues you would choose not to fly the plane without the gap seal.


Well, I long ago decided that I NEVER really have to be anywhere so I am pretty conservative when it comes to impromptu test piloting, weather and equipment failure/reliability.

I would fly out a medical emergency or ferry the plane after removing the other seal but otherwise I’d just get it fixed before I went flying.

In reply to:


Well, I long ago decided that I NEVER really have to be anywhere so I am pretty conservative when it comes to impromptu test piloting, weather and equipment failure/reliability.


And that’s why in spite of your encouraging us to do so, we probably will never get to speculate about how you ended up in an accident. [:)]

In reply to:


And that’s why in spite of your encouraging us to do so, we probably will never get to speculate about how you ended up in an accident.


Although I’ve heard hard work and exercise never hurt anyone… I’m not taking any chances there either!

Hello, lm from Spain, also my SR22 was lose the GAP seal in flight last week, personally l dont like to much fligh in that conditions but…
The only attitude that l feel its when l fligh in automathic, it seem that the aircraft dont find the right level (left and right continiuslly, few degrees but…)
Any way l don`t feel safe.
How you was resolve the problem???

To resolve the problem you should order a new gap seal from Cirrus.
Make sure the surface is very clean (use alcohol) and then apply the new strip. It should also be warm for the adhesive to work properly.
(HOMBRE!

Where are you in Spain?

I will be in Spain for a month this spring to eat Jamon Iberico!

First I will be attending the Spanish Grand Prix in Barca, then in the race in Monaco. Enroute from Barca to Monte Carlo I will go kitesurfing for a week in Bay of Roses. After I will go to the other end of Spain for another week of kitesurfing in in Tarifa.

Maybe we can meet somewhere? Maybe go flying? My friend who now lives in Madrid misses so much private flying!)

Robert

Hi Robert,

how about developping gap seals for the SR20 and get us a few extra knots in cruise, even at the cost of a few knots in stall?

Yup! Got 'em. Good for 2-3 knots.