Had to abort a takeoff

[Chuck Ellsworth]

Landed, put the tailwheel down. The guy in the left
seat put the carb heat in and throttle forward very
quickly.

The problem is obvious and a result of inept instruction when he learned to fly.

[buck82]

It's been a while, two questions: One - wouldn't a weak accelerator pump cause the same thing to happen; regardless of temperature. As I understand it, they are simply plungers with seals that spray/sqeeze extra fuel through the ventury when throttle applications are made? A gradual increse of throttle would allow the weak plunger to keep up, however not to a sudden increase in throttle. perhaps this isn't the way your carburetor works.

Second question; (And I realise you don't have a supercharged engine); Would you go to full power first and leave carb heat on in an aircraft with supercharger/trubocharger ?

[pdw]

... (he) put the carb heat in and throttle forward very
quickly.

The engine coughed and ran roughly, almost certainly
because it went too lean

But why didn't it recover
when I brought the throttle back to half?

OK ... the throttle valve couldn't have been frozen in place with full carb heat on, ... but on this day (-7 / -20) could something (snow/ice contaminant) have been drawn out of the forward intake (which is obviously bypassed when carb heat is on), having loosened thawed (while carb heat was in use) ... dislodging with the sudden carb-heat-off and sametime the full-power airflow ?

[Shiny Side Up]

OK ... the throttle valve couldn't have been frozen in place with full carb heat on, ... but on this day (-7 / -20) could something (snow/ice contaminant) have been drawn out of the forward intake (which is obviously bypassed when carb heat is on), having loosened thawed (while carb heat was in use) ... dislodging with the sudden carb-heat-off and sametime the full-power airflow ?

Ooh! ooh! I know! The contaminant was forced into the intake by some variable crosswind during the take off roll!

[iflyforpie]

No, I am not. Nor do I disagree with IFP. The point is: did you know what IFP told you here before you decided to take-off again ? (an honest question, not an attack)

For me the answer is simple: no, I would not have known that. So I would have called/visited an AME who might have told me that. And then I would have taken off again.

Another thought: would IFP have 'cleared' you to continue to fly with that aircraft without looking at it ? Again, an honest question.

Hey, I'm not sure how I got involved in this.... I'm just an AME.

It is the pilot in command that decides whether the aircraft is in a safe condition for flight. I don't go around my airport with a horse-tail whisk chanting in Sanskrit, blessing every aircraft before takeoff. I only go looking at problems as they are brought to me.

As PIC, CS made the right call of:

a) Aborting the takeoff.

b) Doing a ground check of the engine to ensure it was running properly.

c) (I assume) verifying full power before he was commited to the next takeoff.

Carbs are cantankerous things and one shouldn't get too worked up about an engine coughing if you are pretty sure of the culprit (the poor design of the acceleration pump on aircraft carbs).

[Big Pistons Forever]

I would like to add one extra point to this discussion. If you decide to abort the takeoff make sure you fully close the throttle.

I know of one wrecked aircraft where the engine quit cold when the aircraft was near lift off speed on a shortish runway. The pilot got on the brakes but did not pull back the throttle and as the aircraft was slowing the engine suddenly burst into life and ran up to full power. Startled the pilot let go of the brakes as he frantically pull off the power. By the time he got back on the brakes he could not stop in time and the aircraft went off the runway into a ditch. The aircraft broke its back and the pilot sustained facial injuries when his head hit the instrument panel. (As an aside I will not fly in aircraft that does not have shoulder harnesses)

Finally if you decide to abort don't change your mind. Bring the aircraft to a rapid stop and then assess the situation and if safe to continue clear the runway.

[Colonel Sanders]

I will not fly in aircraft that does not have shoulder harnesses

Tangential point: That sounds awfully good, but the problem is
that there are many older certified aircraft with no paper for
shoulder harness installation.

I suppose you could go ahead and homebrew your own and do
the modification and not put any entry in the logbooks, but that
would be a bit of a "cowboy" move, wouldn't it?

[dahspeers]

How many forum members does it take to change a lightbulb?

What happened, and why, is as clear as day.

You don't know how air/fuel ratios work? Stay on the damn ground. It's fine if your car sputters, and you can pull over and call CAA. Can't do that in the air Princess. You better know what's keeping you up there, how it's doing it, and how to keep it happy.

[Big Pistons Forever]

I will not fly in aircraft that does not have shoulder harnesses

Tangential point: That sounds awfully good, but the problem is
that there are many older certified aircraft with no paper for
shoulder harness installation.

I suppose you could go ahead and homebrew your own and do
the modification and not put any entry in the logbooks, but that
would be a bit of a "cowboy" move, wouldn't it?

Transport Canada has recognized this problem and specifically allows shoulder harnesses to be fitted using the generic practices approved in AC 43 - 13

Perhaps Pilot DAR could elaborate.

I had a friend unfortunately crash his T - Cart. His body jackknifed around the lap belt and his face smashed into the instrument panel. I visited him in the Hospital the day after the accident and it sure was not a pretty picture. Seven operations and over a year of healing later he was more or less back together but the incident made a big impression.

I am certainly not saying that it is wrong to fly an aircraft without shoulder harnesses, just that I choose not to do it, but then the older I get the wider the yellow stripe down my back gets

[Colonel Sanders]

Transport Canada has recognized this problem and specifically allows shoulder harnesses to be fitted using the generic practices approved in AC 43 - 13

Got an AN number? They'd laugh me out of the district
office here if I showed up with AC43-13 as data for that.

How many forum members does it take to change a lightbulb?

Check over on the tailplane lift thread for the answer to that question.
Like watching Honey Boo-boo, it makes me embarrassed.

[Big Pistons Forever]

CAR 551.406 applies. I guess it is up to you to decide how much your face is worth.......

[Colonel Sanders]

CAR 551.406(d): Installation:

Seat belt and shoulder harness installations are classified as major modifications and must be accomplished in accordance with approved or specified data

Yeah. Doing "major modifications" with no paperwork
does not have a bright future.

I guess it is up to you to decide how much your face is worth

Not sure TC really cares that much about my face.

[Big Pistons Forever]

CS. You are correct I was looking at the old 551.406 which specifically addressed fitting shoulder harnesses for aircraft that did not originally have them. It is disappointing to see TC making it harder to fit what both the NTSB and the TSB have repeated pointed out would have greatly reduced the severity of injuries in many accidents.

I sense the hostility level in this exchange escalating so I will refrain from further comments on this non thread related topic.

[Colonel Sanders]

No hostility to you from me. I am however
annoyed that I legally cannot install shoulder
harnesses.

I would logically expect that any guidance from
TC on this subject would be in the form of an
AN such as B037:

http://www.tc.gc.ca/eng/civilaviation/s ... 37-548.htm

However I see no such AN for shoulder harness
installation in older light aircraft.