Jabiru beach emergency landing. Gamtoos area.

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coline
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by coline » Wed Feb 06, 2019 9:37 am

In the interests of safety and further learning - not to hijack the thread.

What if your airplane does not have carb heat? I have flown Rotaxs' for the last 15 years years. No carb heat fitted and no mention or guide what to do in the event of carb icing in the POH. Rotax 912S in particular. I notice some microlights have a mixture lean/rich adjustment fitted but my Tecnam does not. I have flown around the country high, low, inland, coast, summer, winter and engines have never missed a beat, but now in am starting to think what would I do if over the beach at 100 ft and engine slowly lost power. How would i recognise it as carb icing and what could I do to prevent a LOB?

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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by Mrb13676 » Wed Feb 06, 2019 10:32 am

coline wrote:
Wed Feb 06, 2019 9:37 am
In the interests of safety and further learning - not to hijack the thread.

What if your airplane does not have carb heat? I have flown Rotaxs' for the last 15 years years. No carb heat fitted and no mention or guide what to do in the event of carb icing in the POH. Rotax 912S in particular. I notice some microlights have a mixture lean/rich adjustment fitted but my Tecnam does not. I have flown around the country high, low, inland, coast, summer, winter and engines have never missed a beat, but now in am starting to think what would I do if over the beach at 100 ft and engine slowly lost power. How would i recognise it as carb icing and what could I do to prevent a LOB?

Colin
So my manual for the 914 says that carb icing CAN occur and that intake air preheating is the only remedy. Fortunately the turbo iterations get the air preheated in the turbo.. What I find interesting is that there is no remedy in the manual should icing occur in flight.
The POH for the Sling 4 recommends slowing to 75KIAS, reducing throttle to 1/3 and (if possible) leave the icing area. After 1-2min they recommend increasing power slowly.
However, they do say that recovery of engine power may not occur and that a forced landing should be performed in that eventuality.

The internet seems divided on whether icing can occur in the RattleTex or not - my view is that “Ye canna change the laws of physics” so i think it would be a distinct risk.

Something to think about when doing beat ups of the beach....
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by vindog » Wed Feb 06, 2019 10:59 am

I haven't flown the Jabbie for a while. When current on the aircraft, I used to fly at the coast and in the midlands. I was taught that the cylinder head temps were a clue to pending carb icing. What would happen is that either the left or right temp would indicate different temperature from his opposing "neighbor". I would pull carb heat then before any rough running and the temps would then equalize. The carb heat flap made a nice clunk when operated on the ground and was part of the pre-start check.
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by rainier » Wed Feb 06, 2019 11:07 am

heisan wrote:
Tue Feb 05, 2019 2:58 pm
All the MGL EFIS panels allow you to fit a temperature sensor to the carb, which then provides an ice warning when the carburetor throat temp reaches a preset limit.
We have done some experiments at MGL many years ago using Rotax carbs and found the best place to fit a temperature sensor without interfering with the carb itself just behind the throttle valve on the outside of the carb body - fixed with suitable epoxy that can remain a little flexible like Pratleys Wonda Fix. As sensor we used the easily available LM339 with its flat surface in contact with the aluminium of the carb body, helped with a tiny amount of heat transfer grease.

Reflecting temperature changes is very rapid, just seconds while the Epoxy effectively isolates the sensor from any other heat sources that may otherwise lead to incorrect indication. Provided the aluminium surface is cleaned and roughened a bit (it is not very smooth to start with) the Epoxy holds really well. Also quite possible at add some form of simple clamping mechanism should this be deemed necessary.

It is not a perfect means to monitor icing conditions but it does very effectively provide a warning of possible icing conditions if sufficient moisture is present which a proficient pilot can estimate from current atmospheric conditions.
After all, temperature is the primary requirement to create ice, moisture to some or other extent always being present.

There are a number of carb heat kits around that circulate hot coolant around the area behind the throttle flap.

There are two possible areas of ice build up - the first and obvious is behind the throttle flap where flow speed increases with partially open throttle. It should be possible to treat this with frequent changes to throttle settings to dislodge any build up. Most carb heat kits concentrate on this area.
However there is another problem: The main mixture control consisting of a needle in mid flow which is lifted from the main jet cavity by means of a vacuum driven diaphragm. This mechanism can easily be disrupted by just a small amount of ice build up in this area, flow around the needle itself and the decease in temperature at the yet cavity caused by the rapidly evaporating fuel helping to create the ice. The carb kits do not help here - only hot air intake will.

Monitoring the temps in/at the carb cannot fix this of course but at least can give a valuable head up warning. Frequent power changes being the likely and only possible remedy to prevent loss of power or at least to limit it.
The sensor also shows you CHANGES in the temperature directly related to your throttle setting - you can use this to possibly find a "warmer" power setting.
Who said the sky is the limit ? I think not.
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by lessersg » Wed Feb 06, 2019 1:42 pm

For the 912 and 914 Carburetors most of the guys in the cold climates install water jackets.
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by crazeeflya » Fri Feb 08, 2019 11:46 am

jimdavis wrote:
Mon Feb 04, 2019 5:53 pm
Thanks so much Francois. I am actually familiar with the system, and greatly applaud the fact that the hot air is filtered.

I am still not sure what's going on with various reposts of a drastic loss of power. Some folks didn't manage to keep the aircraft flying and others did, but only just, by using carb-heat. Carb-heat should do it's job swiftly and completely if used in good time. Is there a suspicion that the long drawn-out power losses are associated with the heat being applied too late?

Do Jabby engines use vacuum actuated slides/diaphragms in the carbs? and is it possible that the problems could be one slide sticking? Someone reported sudden and extremely violent vibration. That sounds much more like the loss of two cylinders, rather than carb icing.

Anyone any ideas on this?

jim
Hi Jim, the "violent vibration" was of mis-fire like symptoms, yet, after an oil change and inspection (which was why I flew to pmb) - she ran and flew home perfectly, with no anomalies found during the inspection - the symptoms never recurred over the next 150hrs before we sold the aerie.
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by jimdavis » Fri Feb 08, 2019 12:26 pm

crazeeflya wrote:
Fri Feb 08, 2019 11:46 am
jimdavis wrote:
Mon Feb 04, 2019 5:53 pm
Thanks so much Francois. I am actually familiar with the system, and greatly applaud the fact that the hot air is filtered.

I am still not sure what's going on with various reposts of a drastic loss of power. Some folks didn't manage to keep the aircraft flying and others did, but only just, by using carb-heat. Carb-heat should do it's job swiftly and completely if used in good time. Is there a suspicion that the long drawn-out power losses are associated with the heat being applied too late?

Do Jabby engines use vacuum actuated slides/diaphragms in the carbs? and is it possible that the problems could be one slide sticking? Someone reported sudden and extremely violent vibration. That sounds much more like the loss of two cylinders, rather than carb icing.

Anyone any ideas on this?

jim
Hi Jim, the "violent vibration" was of mis-fire like symptoms, yet, after an oil change and inspection (which was why I flew to pmb) - she ran and flew home perfectly, with no anomalies found during the inspection - the symptoms never recurred over the next 150hrs before we sold the aerie.
Ha ha ha. CF that's exactly my point. Carb ice leaves no evidence. I am strongly of the opinion that, for whatever reason, one carb iced and caused its pair of cylinders to stop delivering power, or to deliver reduced power.

All the best

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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by Marius Schrenk » Mon Feb 11, 2019 5:43 pm

jimdavis wrote:
Fri Feb 08, 2019 12:26 pm
crazeeflya wrote:
Fri Feb 08, 2019 11:46 am
jimdavis wrote:
Mon Feb 04, 2019 5:53 pm
Thanks so much Francois. I am actually familiar with the system, and greatly applaud the fact that the hot air is filtered.

I am still not sure what's going on with various reposts of a drastic loss of power. Some folks didn't manage to keep the aircraft flying and others did, but only just, by using carb-heat. Carb-heat should do it's job swiftly and completely if used in good time. Is there a suspicion that the long drawn-out power losses are associated with the heat being applied too late?

Do Jabby engines use vacuum actuated slides/diaphragms in the carbs? and is it possible that the problems could be one slide sticking? Someone reported sudden and extremely violent vibration. That sounds much more like the loss of two cylinders, rather than carb icing.

Anyone any ideas on this?

jim
Hi Jim, the "violent vibration" was of mis-fire like symptoms, yet, after an oil change and inspection (which was why I flew to pmb) - she ran and flew home perfectly, with no anomalies found during the inspection - the symptoms never recurred over the next 150hrs before we sold the aerie.
Ha ha ha. CF that's exactly my point. Carb ice leaves no evidence. I am strongly of the opinion that, for whatever reason, one carb iced and caused its pair of cylinders to stop delivering power, or to deliver reduced power.

All the best

jim
:D Luckily Jim the Jabbi engine has only one Bing CV carby......would not have had it any other way.....two times the trouble.....and cooling. :wink:
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Re: Jabiru beach emergency landing. Gamtoos area.

Unread post by jimdavis » Mon Feb 11, 2019 5:51 pm

Clinton01 wrote:
Thu Jan 31, 2019 8:11 am
Why does the article about this beach landing on News24 end with the following? 'In June, two people were killed when a light aircraft crashed near Midrand, Johannesburg in a residential area. The victims were the pilot and a gardener.'

It's totally irrelevant to the story at hand - over 6 months ago, totally different plane and circumstances, and a very different result. I really get the impression that when News24 have nothing more to say, they just fill space to make articles longer. Maybe the journalist is paid per word or something.
Clinton - you noticed? Ha ha ha :lol:

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