NavList:

Cessna 336 and 337 planes are centerline thrust so do not have the yawing problem when one engine fails but do have the severe reduction in climb performance
 in common with other twins. It may come as a surprise but twins weighing up to 6,000 pounds that have a stall speed of not more than 61 knots are not required to be able to climb on one engine. FAR 23.67 (a)(2) only requires that " the steady gradient of climb or descent" must be determined. An example of this is the Piper Apache which had a pretty good decent rate on one engine. I am not sure that the 336 would climb on one engine since it had fixed gear. The 337 would climb on one but with just the minimum rate required by regulations. Federal Aviation Regulation (FAR) 23.67(a)(1) only requires a 1.5% gradient on one engine. I don't have my 337 manual with me (I am in Paris) but I think its single engine best rate of climb speed (Vyse) was about 90 knots or 9114 feet per minute. 1.5% of this is only a 136 feet per minute rate of climb. I had a case in which the heirs of a pilot who did a touch and go at a one way airport in Paradise California claimed that he had suffered an engine failure caused by my mechanic client's negligence in installing a defective electric boost pump on the rear engine.(Never mind that in a 337 the boost pump is not supposed to be turned on for landing.) Of course, everyone knows you don't do a touch and go on a one way airport since the terrain rises faster than planes can climb. (A one way runway is one on the side of a steep mountain, you land uphill and take off downhill towards lower terrain. You don't do a touch and go, momentarily landing and then taking off again, in the direction of rising terrain.) We were able to prove by witness testimony of the point where he started his takeoff again to the point where he hit the tree that it was impossible for the plane to climb at that gradient on only one engine, both engines had to have been operating to get to the point, near the top of the tree, where the plane impacted. 

A problem unique to the 336/337 was that sometimes the rear engine would quit while waiting for takeoff and the pilot wouldn't k know it and so would attempt to takeoff with only the forward engine which resulted in takeoff accidents. The proper technique is to advance the throttle of the rear engine prior to advancing the throttle of the front engine so that this problem could be identified.

gl




1.1 Critical engine means the engine whose failure would most adversely affect the performance or handling qualities of an aircraft.


Title 14: Aeronautics and Space
PART 23—AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES
Subpart B—Flight
Performance

Browse Previous | Browse Next

§ 23.67   Climb: One engine inoperative.

(a) For normal, utility, and acrobatic category reciprocating engine-powered airplanes of 6,000 pounds or less maximum weight, the following apply:

(1) Except for those airplanes that meet the requirements prescribed in §23.562(d), each airplane with a V_SOof more than 61 knots must be able to maintain a steady climb gradient of at least 1.5 percent at a pressure altitude of 5,000 feet with the—

(i) Critical engine inoperative and its propeller in the minimum drag position;

(ii) Remaining engine(s) at not more than maximum continuous power;

(iii) Landing gear retracted;

(iv) Wing flaps retracted; and

(v) Climb speed not less than 1.2 V_S1.

(2) For each airplane that meets the requirements prescribed in §23.562(d), or that has a V_SOof 61 knots or less, the steady gradient of climb or descent at a pressure altitude of 5,000 feet must be determined with the—

(i) Critical engine inoperative and its propeller in the minimum drag position;

(ii) Remaining engine(s) at not more than maximum continuous power;

(iii) Landing gear retracted;

(iv) Wing flaps retracted; and

(v) Climb speed not less than 1.2V_S1.

Tom Sult wrote:

I agree with what you have said but the crash data for 336/337 is no  
better than other twins.
Thomas A. Sult, MD
IntegraCare Clinic
www.icareclinics.com
tsult@charter.net



On Aug 2, 2009, at 3:58 PM, Greg R. wrote:

  

Not to speak for Gary, but the pusher/puller configuration has  
what's called
"centerline thrust" - i.e. if you lose an engine, the thrust vector  
stays on
the centerline - theoretically making the engine-out procedure  
easier to
handle (ditto for a single-engine, though the engine-out procedure  
is a lot
more cut-and-dried...  ;-)).

Wing-mounted twins have a more-complicated engine-out procedure -  
not only
identifying the dead engine, securing/feathering it (also true of
centerline-mounted engine configs), but also maintaining a slight  
bank angle
to compensate for the thrust imbalance caused by the dead engine.

http://en.wikipedia.org/wiki/Critical_engine

Not sure if the Vmc (minimum-controllable velocity) restrictions  
would apply
to A/C with centerline-mounted engines, that's probably a question  
for Gary.

--
GregR


----- Original Message -----
From: "Greg Rudzinski" <gregrudzinski@yahoo.com>
To: "NavList" <NavList@fer3.com>
Sent: Sunday, August 02, 2009 12:16 PM
Subject: [NavList 9297] Re: Bygrave and Chichester



Gary,

How would the Cessna 336/337 perform if one engine fails? Is there an
advantage to a pusher puller configuration over a single or wing
mounted twins?

Greg

On Aug 2, 11:18 am, Gary LaPook <glap...@pacbell.net> wrote:
    

Well, I would agree with you Douglas, as judged from our  
perspective in
2009, that Chichester may have been "reckless." But as judged from  
the
standards of aviation pioneers almost 80 years ago, I prefer the word
"bold." If you look at early pioneering efforts, Lindberg, Perry, Sir
John Franklin, Columbus etc., they all appear reckless as viewed  
through
our prism of time. But that is what pioneering is all about, taking
      

chances.
    

Regarding you preference for twin engine flying, the accident  
statistics
show that they are more dangerous than singles, pretty
counter-intuitive. Flying a twin when both engines are operating is  
just
like flying a single, it only gets interesting when one quits. Then  
the
pilot must deal with a greatly reduced performance envelope and
asymmetric thrust causing control difficulties. If the pilot  
doesn't do
everything exactly right he ends up crashing and the crash happens  
at a
higher speed than would have occurred in a single. By US  
certification
standards (I expect they are similar in Britain) a single must have a
stall speed below 60 knots while a twin can have a much higher speed.
This means that a pilot trying to crash land a twin must fly above  
the
stall speed resulting in a higher impact speed and much more kinetic
energy to dissipate (varies with velocity squared), can we say "torn
aluminum" and "mangled bodies?" I've litigated airplane crashes for  
the
last twenty years and I have seen my share of bent aluminum and  
autopsy
photos. (BTW, a Cessna 310 Twin fits in a box on a standard pallet,
about five feet square and three feet deep after it impacts the dirt.
Airplanes are mostly air surrounded by an aluminum skin, just like an
empty beer can and they squish just like a beer can..)

After the loss of one engine the airplane has little or no climb
capability. It will only climb or maintain altitude if the pilot does
everything right. If he doesn't get rid or the drag form the flaps,  
the
landing gear and the windmilling propeller immediately then he is  
going
down.

I'll give you some examples. About seven years ago a Cessna 310 was
taking off from Laverne airport just northeast of Los Angeles on July
4, 2002, Independence Day. One engine quit right after takeoff and  
the
pilot did not do everything right and the plane crashed on top of a
bunch of picnickers celebrating Independence Day in the park near the
airport resulting in the deaths of the two occupants of the plane,  
two
deaths of the picnickers and severe injuries for nine other people on
the ground. See the accident report at:
      

http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX01FA152&rpt=fa
    

The left propeller control was found "one inch aft." In order to  
feather
the propeller it is necessary to pull the prop control all the way  
aft,
about eight inches. Since the pilot did not move the prop control all
the way aft the prop did not feather and the plane could not maintain
altitude with the left engine windmilling creating a lot of drag. It
turned out that the pilot had done exactly as he had been instructed.
His instructor's technique for practicing engine out emergencies  
called
for the student pilot to just pull the prop control back one inch to
demonstrate that he had identified the failed engine and that he  
would
have feathered the prop in a real emergency. But in a high stress
situation people do what they have practiced so four dead people,
including two little children, and nine serous injuries.

Another case I worked on involved a Piper Navaho hauling sight seers
around Hawaii. One engine packed it in and because the mechanic had  
not
used the proper method to adjust the wastegate controller on the  
other
engine, the remaining engine was not developing full power so the
airplane could not maintain altitude on the one engine. So even  
though
the pilot was doing everything right he still had to ditch in the sea
near Hilo and one little old lady, celebrating her fortieth wedding
anniversary, rode the plane to the bottom of the sea. See report
at:http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX00FA310&rpt=fa

Another case I worked on involved a Twin Otter powered by two Pratt &
Whitney turboprop engines. The underground fuel tank from which the
airplane had just been refueled was contaminated with water (it  
looked
like mud) and one engine stopped right after the nose was raised  
due to
ingesting the water. The pilot then did everything wrong and  
feathered
the wrong engine, shutting down the one operating engine. This  
resulted
in 16 deaths of the occupants.
See:http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX93FA149&rpt=fa

Having two engines gives one the sense that he has redundant  
systems and
that it is unlikely to have two reliable systems fail at the same  
time.
So, if an engine should fail once every 5,000 hours then the chance  
of
two such engines failing at the same time should be only once every
25,000,000 (5,000 times 5,000) hours. But that assumes that the two
systems are completely independent from each other which is rarely  
the
case. First, obviously, both engines are being operated by the same
pilot and any error on his part can result in the loss of both  
engines.
Both engines received the same fuel so if one tank has contaminated  
fuel
they both do. They were refueled at the same time so if the pilot  
runs
one out of fuel then the other will follow moments later. The same
mechanic worked on both engine and if he screwed up one then he  
probably
screwed up the other one too. I remember watching a Cessna 310 take  
off
from Chicago Midway airport one day. Right after takeoff one engine
failed and the pilot was able to bring it around and land safely. The
plane taxied up to my hangar with one prop stopped and my friend Bill
jumped out and walked right past me. I asked him, as he passed,  
what had
happened and he said he couldn't stop to talk as he had to "go and  
clean
out his shorts." I don't think he was talking figuratively since he  
went
immediately into the men's room. The next day when I saw him I asked
again and he said he was doing a test flight after the mechanic had
adjusted the propeller governor and right after takeoff that one
propeller had gone into feather uncommanded which resulted in the  
loss
of power from that engine. As he was bringing the plane around to  
land
he said that all he could think about was that the mechanic had just
adjusted _both_ propeller governors and he was waiting for the  
other one
to go into feather too.

In the case of over water ferry flights on which the plane is heavily
overloaded with fuel, the single engine ceiling may be below sea  
level.
This means with such a heavy load that the plane cannot maintain
altitude if just one engine fails and a ditching is inevitable. In  
this
case a twin is quite a bit less safe than a single since with two
engines you have twice the probability of an engine failure, 2 per  
5,000
hours using my prior example.

gl

douglas.de...@btopenworld.com wrote:
      

My interest in the Bygrave helical slide rule too Gary, was  
stimulated
        

when I read Chichester's book 'The Lonely Sea and the Sky' many  
years ago.
    

I have been hoping ever since to find one, perhaps one of them would
        

turn up in an antique shop or 'car boot sale', but now realise that  
fond
dream is far from ever becoming a reality.
    

It is very strange that they are now so incredibly rare  
considering they
        

must have been made in reasonably large numbers from the early  
1920's up to
the mid 1930's, and were also an official piece of navigating 'kit'  
for
aircraft navigators in that period for the RAF, so must have been  
made in
fairly large numbers rather than just a relatively few for  
experimental
purposes. They were also available to buy privately. So what  
happened to
them all? It's most odd.
    

Even the most arcane scientific apparatus and instruments are  
usually
        

preserved or survive in private hands to be sold on or given away to  
others
rather than just binned.
    

Are all those RAF Bygrave slide rules still locked away in some old,
        

musty, forgotten RAF or government store at the back of dusty shelves
awaiting some storekeeper to find them and be told to put them in an  
auction
of ex-government surplus. (Still dreaming you see !).
    

Whilst the skill and amazing endeavour of what Chichester achieved  
is
        

not to be denied an any way, (and you have now confirmed by your own
practical flying test in a Tiger Moth); which was immediately  
apparent to me
when I read of the exploit, and it has continued to amaze me still -  
with
what he wrote I was also filled with the astonishment and feelings  
that
Chichester was idiotically reckless in what he did,..(I think) to  
the point
of insanity.
    

Given that he writes in a style which is deliberately meant to  
make his
        

story not just interesting but no doubt boost his (Chichester's)  
reputation,
and sales of the book, and hopefully have the reader clutching the  
book with
white knuckles in anticipation of events unfolding; nevertheless, he  
exposes
a devil-may-care attitude of quite serious stupidity and ignores  
issues of
high importance which any right-thinking person would not consider
reasonable, and certainly not anyone who knows anything about flying  
and the
consequences involved in flying solo in a single engined aitrcraft  
with a
'dodgy' engine over large stretches of water.
    

----------
        

I had a personal friend who taught me to fly, he was the Chief  
Flying
        

Instructor at Bembridge flying school, and who very nearly lost his  
life
when the donkey of the Cessna 150 stopped en route, mid - Solent, as  
he was
flying back to Bembridge from Goodwood, (The Solent is the sea -  
only four
miles of water between the Isle of Wight and the mainland) -and after
turning downwind towards the mainland to maximise his ground  
traverse, he
did not make it and was...
    

read more »