Crash at Plett airport (SF25 on 2 Dec 2019)

What your instructor never taught you. Continuing your education and learning from others. Flight safety topics and accident/incident discussions.

Moderator: Moderators

spokes
Post Take off checks
Posts: 225
Joined: Sat Jul 06, 2019 1:39 am
Closest Airfield: Siver Creek
Location: Rustenburg
Has liked: 19 times
Been liked: 82 times

Re: Crash at Plett airport.

Unread post by spokes » Wed Dec 04, 2019 8:37 pm

I see on the media the pax also passed on? Is it old news or hopefully fake?
User avatar
Ugly Duckling
Seven Thousand
Seven Thousand
Posts: 7040
Joined: Sat Mar 18, 2006 2:24 pm
Closest Airfield: Brakpan Benoni FABB
Location: Waterkloof
Has liked: 654 times
Been liked: 573 times

Re: Crash at Plett airport.

Unread post by Ugly Duckling » Wed Dec 04, 2019 8:38 pm

spokes wrote:
Wed Dec 04, 2019 8:37 pm
I see on the media the pax also passed on? Is it old news or hopefully fake?
Unfortunately correct
Paul Sabatier EAA Ch 575, SSSA, ERGC, ERFC, AeroClub
Long time Cygnet builder
The object is to fly, it does not matter what the object is!
i24
Flight Planning
Posts: 7
Joined: Sat Dec 17, 2011 11:53 pm
Has liked: 0
Been liked: 18 times

Re: Crash at Plett airport.

Unread post by i24 » Wed Dec 04, 2019 10:14 pm

Some speculation. I am not familiar with the accident site and I never knew the pilot.

But I have been instructing in K7 and K13 gliders for over 25 years and I did my TMG rating in UUA. I fly at Worcester where we regularly fly the fabric gliders in winds gusting up to 50km/h (and glass ships in stronger winds).

I think with a pilot of this experience in a low wing loading fabric glider, the wingtip touching the ground while attempting a coordinated turn at low altitude resulting in a "cartwheel" crash is more likely than a spin. (I have witnessed 2 crashes like that).

Otherwise a wind gust causing the glider to drop out of the sky and hit the ground, maybe with a wing low, is a possibility.

The suggestion that all TMG landings should be made with the engine on obviously was not made by a glider pilot. In gliding, we plan circuits with excess energy, which is then dissipated with airbrakes. Airbrakes are more reliable than engines, so a glide approach is safer. In particular the Limbach engined Falkes have very modest power. If you find yourself in strong weather and need power to save yourself the Limbach might not be enough.

In high winds we use a "high wind speed approach" technique. A very steep final approach, with high airspeed and full airbrakes, rounding out late and flaring in ground effects below the worst of the gusts and wind shear. It is technique that requires training, practice and currency but allows us to fly in strong wave conditions. The Falke is not the best glider for this as it does not have very powerful airbrakes and the u/c is higher due to the prop, so you have to flare higher. We normally only use these approaches in strong NW storm winds, which are often >40 knots at circuit height and result in strong windshear and unpredictable gusts. SE winds are often low level sea breezes which decrease with speed above circuit height and a circuit planned to not stray downwind of the airfield is usually sufficient.

Regarding the operation's commercial license status - which I understand was in place. Operators who regularly flout regulations are often associated with poor safety records, but adding a ton of additional paperwork to an operator who already exercises good airmanship is unlikely to significantly reduce their accident risk.

A final comment. If a pilot with this experience and skill can get caught out, we have to accept that it can happen to any of us. You can never drop your vigilance.

Lets see if the investigation discovers a technical fault.
These users liked the author i24 for the post (total 18):
John BoucherIKTAVjimdavisDragonChristopherDurr PietersACE MAN10tpegMrb13676KEOTFDZiggiLearjetexcolonialSea RescueVoloChrisWilhelmMosehuus
User avatar
jimdavis
10000 and still climbing
10000 and still climbing
Posts: 16643
Joined: Thu Jun 19, 2008 7:46 am
Closest Airfield: FAGG
Location: Wilderness
Has liked: 714 times
Been liked: 858 times

Re: Crash at Plett airport.

Unread post by jimdavis » Wed Dec 04, 2019 10:28 pm

Kobus Luttig wrote:
Wed Dec 04, 2019 5:00 pm
Chalkie wrote:
Tue Dec 03, 2019 9:28 pm
Jack Welles wrote:
Tue Dec 03, 2019 4:05 pm
I didn't know the fellow and didn't know the operation but it seems to me that an awful lot of emphasis is being placed on the paperwork being in order (which is important, of course). He was also really well qualified as a pilot with extensive experience.
I did know the man. You could not get a better, more conscientious, more qualified, more caring, more supporting, more competent pilot.

All the BS about licence is BS. They had to jump through many hoops for an extended time to gain their CAA approval.

I hereby resign from avcom.
I am Afrikaans but I will try my best.
Chalkie, please come back. I've learned more from AVCOM and all your guys in my 29 years of flying then all of my training combined.
I also enjoy all the other discussions. You have to ignore some of them, but its no big deal.
Please guys, can we please cool it a bit. Sometimes we take speculation too far and fast. If I am ever involved in an accident or incident please don't speculate. It will purely be because I was sleeping on the job.
:(
What a wonderful first post Kobus - keep it up, I like your style! :D =D> :D

jim
These users liked the author jimdavis for the post:
Sea Rescue
"PPL Manual"
"Flight Tests"
"So Others May Live"
"Flying in Africa" Vol 1
"Flying in Africa" Vol 2
Look inside these books, or buy them at: www.jimdavis.co.za.
svenolivier
ATC Delay
Posts: 119
Joined: Thu Dec 10, 2009 2:53 pm
Has liked: 6 times
Been liked: 16 times

Re: Crash at Plett airport.

Unread post by svenolivier » Wed Dec 04, 2019 11:56 pm

at Worcester (as was mentioned earlier) we do fly in some high wind conditions - we have developed a technique for doing so which is particularly useful for lower wingloading aircraft. I hope i can explain the thinking behind the technique properly.
In a high wind gradient, if you are too slow, pushing the nose down, does not necessarily result in you regaining airspeed, as the wind speed reduces just as you are converting your height into kinetic energy - the lower windspeed effectively deprives you of the energy you would ordinarily gain by pushing the nose down. if you are unluckly you will stay slow or stalled till you hit the ground.

If this sounds wrong to you, consider how quickly you climb on take off if the wind gradient is steep - i am certain many of you would have experienced this - the reverse happens when you descend.

So it is imperative to have a far higher approach speed, together with full airbrakes (if you are in a Falke as Stew flew) to ensure a (very) rapid descent rate.

Sven
These users liked the author svenolivier for the post (total 8):
Durr PietersjimdavisSTEELVoloDragonSea RescueChrisWilhelmMosehuus
User avatar
jimdavis
10000 and still climbing
10000 and still climbing
Posts: 16643
Joined: Thu Jun 19, 2008 7:46 am
Closest Airfield: FAGG
Location: Wilderness
Has liked: 714 times
Been liked: 858 times

Re: Crash at Plett airport.

Unread post by jimdavis » Thu Dec 05, 2019 5:26 am

svenolivier wrote:
Wed Dec 04, 2019 11:56 pm
at Worcester (as was mentioned earlier) we do fly in some high wind conditions - we have developed a technique for doing so which is particularly useful for lower wingloading aircraft. I hope i can explain the thinking behind the technique properly.
In a high wind gradient, if you are too slow, pushing the nose down, does not necessarily result in you regaining airspeed, as the wind speed reduces just as you are converting your height into kinetic energy - the lower windspeed effectively deprives you of the energy you would ordinarily gain by pushing the nose down. if you are unluckly you will stay slow or stalled till you hit the ground.

If this sounds wrong to you, consider how quickly you climb on take off if the wind gradient is steep - i am certain many of you would have experienced this - the reverse happens when you descend.

So it is imperative to have a far higher approach speed, together with full airbrakes (if you are in a Falke as Stew flew) to ensure a (very) rapid descent rate.

Sven
Hi Sven - neatly explained. That makes a lot of sense =D> =D> =D>

jim
These users liked the author jimdavis for the post:
STEEL
"PPL Manual"
"Flight Tests"
"So Others May Live"
"Flying in Africa" Vol 1
"Flying in Africa" Vol 2
Look inside these books, or buy them at: www.jimdavis.co.za.
spokes
Post Take off checks
Posts: 225
Joined: Sat Jul 06, 2019 1:39 am
Closest Airfield: Siver Creek
Location: Rustenburg
Has liked: 19 times
Been liked: 82 times

Re: Crash at Plett airport.

Unread post by spokes » Thu Dec 05, 2019 5:33 am

I was taught to add half the gusting speed to your normal approach speed in power flying. As another famous glider pilot used to say, "airspeed is half a life"

In this situation though all of what we say must have been second nature to the pilot.
User avatar
Mrb13676
1k poster
1k poster
Posts: 1029
Joined: Mon Jun 05, 2017 3:20 pm
Closest Airfield: FASY
Location: Zone outbound
Has liked: 294 times
Been liked: 169 times

Re: Crash at Plett airport.

Unread post by Mrb13676 » Thu Dec 05, 2019 7:12 am

i24 wrote:
Wed Dec 04, 2019 10:14 pm

A final comment. If a pilot with this experience and skill can get caught out, we have to accept that it can happen to any of us. You can never drop your vigilance.

Lets see if the investigation discovers a technical fault.

A great post with this very pertinent comment. If we get nothing else from this event, let it be that we all understand this point very well.
These users liked the author Mrb13676 for the post (total 2):
apollo11Flooi
Mike Blackburn
ZU-IBM - Sling4 Turbo s/n 009
ESTLEC
Rolling
Posts: 153
Joined: Thu Jan 26, 2006 9:09 pm
Location: JHB
Has liked: 1 time
Been liked: 15 times

Re: Crash at Plett airport.

Unread post by ESTLEC » Thu Dec 05, 2019 8:39 am

Agree totally Sven ,

Learning to glide makes you a safer pilot, every pilot should try it.
These users liked the author ESTLEC for the post (total 2):
DragonScrapyard Dog
TAKE OFF IS OPTIONAL ?
i24
Flight Planning
Posts: 7
Joined: Sat Dec 17, 2011 11:53 pm
Has liked: 0
Been liked: 18 times

Re: Crash at Plett airport.

Unread post by i24 » Thu Dec 05, 2019 6:32 pm

svenolivier wrote:
Wed Dec 04, 2019 11:56 pm
at Worcester (as was mentioned earlier) we do fly in some high wind conditions - we have developed a technique for doing so which is particularly useful for lower wingloading aircraft. I hope i can explain the thinking behind the technique properly.
In a high wind gradient, if you are too slow, pushing the nose down, does not necessarily result in you regaining airspeed, as the wind speed reduces just as you are converting your height into kinetic energy - the lower windspeed effectively deprives you of the energy you would ordinarily gain by pushing the nose down. if you are unluckly you will stay slow or stalled till you hit the ground.

If this sounds wrong to you, consider how quickly you climb on take off if the wind gradient is steep - i am certain many of you would have experienced this - the reverse happens when you descend.

So it is imperative to have a far higher approach speed, together with full airbrakes (if you are in a Falke as Stew flew) to ensure a (very) rapid descent rate.

Sven
Some more comments on the high wingspeed approach. We normally use this in conditions when there is a strong wind gradient and possible turbulence with horizontal and vertical gusts below 500'. In these conditions I have seen aircraft loose (or gain) 50' on short finals, within seconds. The most dangerous zone is between ground and 50'.

- Vertical gusts start or finish as horizontal gusts at ground level. The less time you spend in the gust zone, the lower the probability of getting caught by a gust and the closer to ground that you flare, the less chance of being caught by a vertical gust while flaring.

- The high approach speed leaves a big margin over stall speed. If your airspeed drops suddenly it does not leave you wafting around near stall speed in the gust zone (basically Sven's comment above).

- Full airbrakes increases the effective wing loading, as part of the wing is "blanked off" by the airbrakes, the rest has to generate more lift to support the aircraft. This improves stability in strong turbulence.

- With full airbrakes, you have lots of energy available, simply by closing the airbrakes, we cant do a go around but we can delay the landing for a while if it becomes necessary (but the 2nd landing attempt has to be made with less excess energy, which is not so comfortable).

- Overshooting the runway is not a concern with these wind conditions the glider stops very quickly after landing, thus there are no negative side effects. You just need to flare before you reach ground level and the natural reaction is to flare too soon (you see a lot of runway approaching quickly). "Practising" this without sufficient wind, will result in a long landing roll.

But you do need a proper briefing and it is best to watch other gliders do it before trying it dual. I don't know if the weather conditions during the Plet accident were appropriate for this technique.
homebuilt
1k poster
1k poster
Posts: 1062
Joined: Fri Mar 15, 2013 3:36 pm
Closest Airfield: FAEL
Location: South Africa
Has liked: 0
Been liked: 39 times

Re: Crash at Plett airport.

Unread post by homebuilt » Thu Dec 05, 2019 9:47 pm

A number of years ago the wind in East London was gusting to 60 odd knots at the airport. We landed on the cross runway almost directly into the wind with no problem. Shortly thereafter a Maule came in to land. The aircraft was not local and so chose to land on the main runway with dire consequences. Low to the ground on final, a gust caught the wing and corkscrewed the aircraft whereafter the other wing struck the ground and the aircraft cartwheeled to a stop. The occupants were badly injured and the aircraft was a write off. The wind on rw29 comes past the hangars and terminal building and parked aircraft and swirls in all directions and this is the reason that we normally use the cross runway in high wind conditions; to diminish the effect of the swirling winds.
Now I dont know the airfield in question at all but maybe there are some obstacles that could cause just this type of wind scenario. This aircraft is much lighter than the aircraft we normally fly (and the Maule in this case) so it would stall quicker in gusty conditions and I am sure lift a wing much easier. What I am saying is that no matter how good the pilot, there is always the chance that he/she could get caught out by a gust and at that low level, there is absolutely nothing one can do to save the situation.
I also think of our own aerobatics ace who while flying in formation under a bridge, hit turbulence and stuck a wheel into the drink and this nearly cost him his aircraft. All these above scenarios are reasonable to good pilots who got caught out so suddenly by something they never expected so we need to remember that this is the reason we partake on this forum; to learn so that one day, maybe, hopefully, the knowledge learned can save our bacon.
A big thank you to those stalwarts who are always there to correct, teach and share with us.
These users liked the author homebuilt for the post (total 4):
Ugly DucklingMouserVoloGus
Romeo E.T.
Niner Tousand
Niner Tousand
Posts: 9123
Joined: Wed Nov 16, 2005 10:49 pm
Closest Airfield: FAJS
Location: JHB INTL/Kpt Park/Rand Apt
Has liked: 33 times
Been liked: 255 times

Re: Crash at Plett airport.

Unread post by Romeo E.T. » Thu Dec 05, 2019 10:29 pm

homebuilt wrote:
Thu Dec 05, 2019 9:47 pm
A number of years ago the wind in East London was gusting to 60 odd knots at the airport. We landed on the cross runway almost directly into the wind with no problem. Shortly thereafter a Maule came in to land. The aircraft was not local and so chose to land on the main runway with dire consequences. Low to the ground on final, a gust caught the wing and corkscrewed the aircraft whereafter the other wing struck the ground and the aircraft cartwheeled to a stop. The occupants were badly injured and the aircraft was a write off.
that would be this accident viewtopic.php?f=9&t=159230
sometimes we suffer a bit from C.R.A.F.T. sickness..Can't Remember A F@#%ing Thing

https://www.facebook.com/ralf.t.schulz
User avatar
AnAV8R
Reaching GFA
Posts: 268
Joined: Fri Jul 16, 2010 11:10 am
Has liked: 13 times
Been liked: 14 times

Re: Crash at Plett airport.

Unread post by AnAV8R » Fri Dec 06, 2019 5:23 pm

The popcorn munchers may enjoy this, and the handbag bashers may be upset, but please bear with me as I play devils advocate on something that concerns me.
I’m not being negative to Stu, (RIP fellow aviator, and sincere condolences to the families of Stu…..and passenger families), but just putting forward some facts and research I’ve looked into.
I apologise in advance if this post sounds damning, but we are here to learn are we not?

There is a lot of consensus on this forum, call it speculation, that there was a stall situation that caused this tragic incident, and I would like to add my 2c worth, so take it as you wish, I’m not prepared to fight about my opinion.

We all know that stall speed is proportional with the aircraft weight. Stall speed increases, as the weight increases, accepting that let’s look at the weight of the aircraft at the time of the accident.
The SF25 empty weight is 345 Kg’s
Max gross weight is 540 Kg’s
Deducting from that information we have a 195 Kg’s payload.

So what was the “payload”?
Looking at the picture of Stu posted, I would say his weight about 85 to 90 Kg’s?
Information received (cannot verify?) was that the pax weight was 125 kg’s.
Well do the math and see we already 20 Kg’s over gross weight.
Now let us add some fuel. How about 30 Kg’s….? (I have heard, subject to correction, that there were “Long range tanks” fitted? And I have no idea how much fuel was onboard!)
And now we sitting at 50kg’s over gross weight!!

So what was the actual stall speed in that condition?
Vs new = Vs old x √ new weight / old weight
Vs at gross weight is 65 Kmh
Vs at new weight is 68 Kmh

Now take into consideration the age of the ASI and was it recently calibrated for accuracy?
Take into account the gust factor?
Take into account the terrain / turbulence / wind shear? (Off topic, but pilots should be very cognisant of micro-meteorology and the effect when flying light aircraft !)

With the above scenario, and assuming the approach was with power off, wind is gusting, bumpy ride, low on approach, trying to extend the glide, it’s not a comfortable situation to be in!
So lets assume the following.
The aircraft is flying in a gust of 25 kts, the aircraft is flying 5 kts above “published stall speed” (70 kmh – 38 kts – which is published best glide speed) to extend the glide as indicated by the ASI (If correct – calibration?)
The gust stops, down to 15 kts…..with the “indicated air speed” of 70 kmh (38 kts)
The aircraft is now on the edge of a stall condition….in fact if the above conditions did exist…in a stall…
The aircraft is above gross weight thus increasing the stall speed, thus aggravating the situation.
The published approach speed is 85 kmh (46 kts), if the approach was flown at this speed the aircraft would still be in a stall situation.

At low altitude, not matter how experienced the pilot is, recovering would be near nigh impossible!

Just saying….speculation…?
This is what I’ve heard so please don’t bash me…..
These users liked the author AnAV8R for the post (total 3):
SteveJohnnyJetPeter Bailey
User avatar
Wingnutter
Too Tousand
Too Tousand
Posts: 2394
Joined: Fri Jun 10, 2005 11:14 pm
Closest Airfield: Chek Lap Kok VHHH
Location: Hong Kong
Has liked: 46 times
Been liked: 85 times

Re: Crash at Plett airport.

Unread post by Wingnutter » Sat Dec 07, 2019 5:58 am

Was it UUA that crashed? Did my motor glider conversion in that aircraft when it was operated by the Cape Gliding Club and flew a number of hours in her.

It's sobering how many of the GA aircraft in my logbook have been destroyed, many in fatal accidents, 2 this year,
If nothing else works, a total pig-headed unwillingness to look facts in the face will see us through.
User avatar
Dragon
Straight and Level
Posts: 546
Joined: Mon Aug 08, 2011 11:29 pm
Closest Airfield: Morning Star
Location: In the Sky - Western Cape
Has liked: 242 times
Been liked: 84 times

Re: Crash at Plett airport.

Unread post by Dragon » Sat Dec 07, 2019 11:40 am

AnAV8R wrote:
Fri Dec 06, 2019 5:23 pm
The popcorn munchers may enjoy this, and the handbag bashers may be upset, but please bear with me as I play devils advocate on something that concerns me.
I’m not being negative to Stu, (RIP fellow aviator, and sincere condolences to the families of Stu…..and passenger families), but just putting forward some facts and research I’ve looked into.
I apologise in advance if this post sounds damning, but we are here to learn are we not?

There is a lot of consensus on this forum, call it speculation, that there was a stall situation that caused this tragic incident, and I would like to add my 2c worth, so take it as you wish, I’m not prepared to fight about my opinion.

We all know that stall speed is proportional with the aircraft weight. Stall speed increases, as the weight increases, accepting that let’s look at the weight of the aircraft at the time of the accident.
The SF25 empty weight is 345 Kg’s
Max gross weight is 540 Kg’s
Deducting from that information we have a 195 Kg’s payload.

So what was the “payload”?
Looking at the picture of Stu posted, I would say his weight about 85 to 90 Kg’s?
Information received (cannot verify?) was that the pax weight was 125 kg’s.
Well do the math and see we already 20 Kg’s over gross weight.
Now let us add some fuel. How about 30 Kg’s….? (I have heard, subject to correction, that there were “Long range tanks” fitted? And I have no idea how much fuel was onboard!)
And now we sitting at 50kg’s over gross weight!!

So what was the actual stall speed in that condition?
Vs new = Vs old x √ new weight / old weight
Vs at gross weight is 65 Kmh
Vs at new weight is 68 Kmh

Now take into consideration the age of the ASI and was it recently calibrated for accuracy?
Take into account the gust factor?
Take into account the terrain / turbulence / wind shear? (Off topic, but pilots should be very cognisant of micro-meteorology and the effect when flying light aircraft !)

With the above scenario, and assuming the approach was with power off, wind is gusting, bumpy ride, low on approach, trying to extend the glide, it’s not a comfortable situation to be in!
So lets assume the following.
The aircraft is flying in a gust of 25 kts, the aircraft is flying 5 kts above “published stall speed” (70 kmh – 38 kts – which is published best glide speed) to extend the glide as indicated by the ASI (If correct – calibration?)
The gust stops, down to 15 kts…..with the “indicated air speed” of 70 kmh (38 kts)
The aircraft is now on the edge of a stall condition….in fact if the above conditions did exist…in a stall…
The aircraft is above gross weight thus increasing the stall speed, thus aggravating the situation.
The published approach speed is 85 kmh (46 kts), if the approach was flown at this speed the aircraft would still be in a stall situation.

At low altitude, not matter how experienced the pilot is, recovering would be near nigh impossible!

Just saying….speculation…?
This is what I’ve heard so please don’t bash me…..
Having no firsthand knowledge of the applicable loadsheet and in any case not wanting to address the legalities of the above argument (I will leave that to others) allow me to discuss the practicalities.

My point is this: an inexperienced pilot would load up an aircraft to the max and then treat her the same as an empty aircraft and possibly get into troubles it is true, but not someone with Stew’s experience. He is used to pushing speeds up for heavy aircraft and decreasing them for light weights and it would have been second nature for him not to fly on the numbers for the approach if he knew he was heavy. For what it’s worth the glide penetration would have been better and with a higher wing loading the gust handling capabilities would have improved being heavier too, the only provisor being that the speeds be stepped up.

This is why real gliders get their wings filled with water and why model flyers when the winds get too gusty during slope soaring, scratch around for a stone or a chunk of lead to prestik into their model glider as a quick fix. There are times when heavy is good.

-edited : I am not promoting flying overweight, just explaining that I don’t think if present it would have caused enough problems to have caught Stew with his pants down.
Last edited by Dragon on Sat Dec 07, 2019 4:35 pm, edited 1 time in total.

Return to “Academy & Flight Safety”