ATSB report on loss of performance involving DH82A

[Old Akro]

I like flying Tiger Moth's. They are a great aeroplane. But I have never heard of Tiger Moth & performance used in the same sentence before. So, I read this report because of the title. Loss performance involving DH82A (Tiger Moth). I'm thinking, when did it have performance? Where did it go?

Paraphrasing a fair bit. This is 2 guys in a Tiger taking off to do some formation flying and the Tiger failed to outclimb a tree. The fact that neither guy was seriously injured was in part I suspect due to some nice flying and partly testament to the wood structure of a Tiger (and probably partly due to its slow flying speeds).

So, why did the Tiger lose performance? Was there an engine problem? What was the engine condition like (what was its time in service?) Was there a fuel problem? Was there a local wind / downdraft issue? Was there a problem with the functioning of the slats? Did the engine test run properly after the accident?

If you think that addressing any of these issues might be germain to the report you'd be disappointed. Instead the safety message is about the importance of crew communication.

The ATSB places this emphasis on crew communication because there was some confusion about whether the aircraft was operating with wide open throttle or at 2150 rpm. Its been a year or ten since I flew a Tiger so I went to my copy of Bramson & Birch's "The Tiger Moth Story" which says that the Tiger climbs at 1950 rpm. The NZ Tiger Moth Club's on line handing notes confirm this, but another thread on pprune refers to 2100 rpm. Either way, it seems that 2150 rpm should have been enough. So why is the ATSB hung up on this point of crew communication? It barely seems relevant. And more importantly, why to they arbitrarily exclude all other factors?

In fact, why is there a report at all on an accident of a private aircraft that does not involve serious injury and (I hope) the aircraft will be rebuilt? There are other private accidents involving fatalities that do not get investigated at all and accidents of significance that take 2 years or more for a report.

I don't know who the pilot(s) are, but I hope they are flying again and that the Tiger is / can be repaired.

[T28D]

It is the ATSB that needs to be repaired/replaced

[Jack Ranga]

Yes, have just started flying the tigermoth & to remove the performance issues mentioned we just cut 2 trees down at the aerodrome :ok:

[PA39]

Something to justify the meagre existence of the boffins. So what...it didn't clear trees, no need for a royal commission. Perhaps the moth should have had a RAM conversion??

[Ex FSO GRIFFO]

Tch Tch Mr 'A'....

Tigers and 'performance' used in the same sentence - indeed!!

Re: "the pilot flying noted that the aircraft was not climbing as expected and, realising that full power was not selected, applied full power by moving the throttle fully forward and lowered the nose of the aircraft slightly to gain speed."

Sounds 'sus' like... (SPECULATION!!!...Warning...Warning....Will Smith...)
- The pilot flying did not push the throttle fully forward - and in the case of 'formation flying' this would be the case, but maybe just 'not enuf'..??

- Or, pushed it to a 'normal' formation T/O position, then maybe took his hand orf the throttle, for whatever reason, and it crept back..??
Friction Nut..??

He was the lead aircraft. so propwash / downwash from other aircraft in formation probably not the prob...?

Re: "Was there a problem with the functioning of the slats?

Usually not a problem, as they open 'auto' about 3 kts prior to the stall
and rarely in the climb, but yes, they could open in the climb, and then they are usually a 'stall warning', but, by then the speed (IAS) would have to be
fairly 'low' and the machine would feel 'mushy'...

If kept locked, then the only stall warning is the low IAS, (normal straight
climb out - & in formation - probably the case)...and that 'mushy' feel...

If he was the lead, then how did the other members fare..??

Not taking the p155 out of you, as I own a Tiger, but ours has the Series 10 Mk2 engine wif de extra 15 HP.... (Chippy Engine), so the 'performance' is
'not bad'......For a Tiger....

Food for thought is all....and, I have to agree with you...that 'report' is certainly lacking in the detail of questions - let alone the answers...???
:ok:

[VH-XXX]

GIGO - Garbage in, garbage out.

If you get a half baked story that has potentially been told that wasn't entirely the truth, you'll get a half-arsed explanation as to what happened.

(Note - this is a general comment and not related to the accident referenced by this discussion)


I know of a DH82 that crashed on takeoff and was written off. The pilot said that the engine lost power and the passenger gave a description that pointed directly at a stall due to lack of airspeed on takeoff. It got written up as engine failure.

[jas24zzk]

Why do people fly these tigers when you can taxy them faster?

:E

[Wanderin_dave]

Why do people fly these tigers when you can taxy them faster?

Because it takes more skill to taxy a Tiger than it does to fly a Cessna! :}

[CHAIRMAN]

Why do people fly these tigers when you can taxy them faster?
Not right. Griffo is on the money. With a decent HP engine, they perform very well. Take off and landing distance is very short.
The issue is not so much one of power, but one of drag. If the power disappears, drag reduces the airspeed very smartly.
As for taxying without brakes, slower is better:{

[dogcharlietree]

With a decent HP engine, they perform very well. Take off and landing distance is very short.

NOTHING at all to do with engine hp. It all has to do with what pitch prop you have on it.
If you have a cruise prop (course pitch) there is now way in hell you will get 2150rpm on takeoff. Geezus, it only gets off the ground due to the curvature of.... Whereas if you have a fine pitch prop, entirely different story. :*

[Ex FSO GRIFFO]

OI just dunno Charlie....Been a 'Fair While' since you've experienced the joys of it all..??


Yes, there are various pitch props available...but they all have 'trade offs'....

The Fine Pitch you mention will get you orf de ground better, but you just won't go anywhere 'in a hurry' afterwards - good for crop-spraying I'm told.

:rolleyes:

[dogcharlietree]

True, Griffo. They tell me that these days they have a tail-wheel and brakes ;)
Not a real Tiger :=

[Kharon]

1994 ATSB (http://www.atsb.gov.au/publications/investigation_reports/1994/AAIR/pdf/ASOR199401106.PDF)on a Tiger incident.

2013 ATSB (http://www.atsb.gov.au/publications/investigation_reports/2012/aair/ao-2012-169.aspx)on a Tiger incident.

Neither is terribly long, but the time to make the comparison is worth the trouble, for example:-


1994) - 1.7 Aircraft performance

The Tiger Moth is a low powered, high drag aircraft. During the investigation it was found that a wing-walker would increase the drag by 27%. This increased drag would reduce the aircraft's maximum cruise speed from 75 kts to 58 kts.

The wing-walking frame fitted to the accident aircraft was manufactured for and fitted to Tiger Moth VH-GVA in January 1990. This aircraft was subjected to flight tests (supervised by the Civil aviation Authority) to assess, in accordance with Flying Operations Instruction 27-2, its performance and handling characteristics. The investigation found no evidence that any performance calculations were made prior to the flight tests.

During the initial flight test, VH-GVA was fitted with a propeller having a 4 ft 6 in pitch. On a subsequent flight, with a 4 ft 2 in pitch propeller fitted, the rate of climb improved and it was established that the particular aircraft/engine/propeller/pilot combination achieved a best initial climb speed of 53 kts. The maximum attainable straight and level speed was 63 kts. The normal climb and cruise speeds are 59 kts and 75 kts respectively. The accuracy of the test results could not be determined as there was no requirement to calibrate the instrument system on the aircraft prior to the tests.

The flight tests found that before being fitted with the frame, VH-GVA accelerated from 50 kts to 70 kts in 12 seconds. With the frame fitted and a dummy installed, the aircraft took 24 seconds to accelerate from 50 kts to its maximum straight and level speed of 63 kts. There was also a noticeable rudder buffet that was later found to be reduced if the wing-walker stood with feet apart.

The wing-walk frame was later sold to the pilot of VH-UNA, who fitted it to his aircraft in February 1992, in accordance with an engineering order approved by the design engineer involved with the original installation on VH-GVA.

Along with the engineering order, the pilot received a copy of Civil Aviation Authority letter V131/24/34, dated 28 March 1990, which required among other things that for all wing-walking flights the propeller fitted to the aircraft should be of 4 ft 2 in pitch. The propeller fitted to the aircraft at the time of the accident was Part Number DH5220/H/26 and of 4 ft 11 in pitch. There was no record of a fine-pitch propeller having been fitted to VH-UNA since the wing-walking frame was initially fitted in 1992.

There is no regulatory requirement for the owner of an aircraft to inform the Authority of any approved modification being fitted to an aircraft. Also, for this particular modification, there was no requirement for the flight manual to be amended to detail the conditions surrounding the installation of the modification. Consequently, the Authority's file for the aircraft did not contain details of the fitting of the frame to the aircraft.

The first entry in relation to the wing-walking equipment occurred one year after installation when an airworthiness survey of the aircraft found irregularities in the procedures used during installation. Certification for manufacture of the frame had not been made and weight and balance considerations had not been addressed. The Authority's file did not contain a copy of the Authority's own letter that required a fine-pitch propeller to be fitted, nor did the survey disclose that an incorrect propeller was installed.

The design engineer who completed the original work on VH-GVA and authorised the installation onto VH-UNA is based at Bankstown, and his file was held in the Bankstown, NSW office of the Authority. The aircraft was based at Archerfield, Qld and its file was accordingly held in the Archerfield office of the Authority. There is no system within the Authority requiring that modifications approved by a design engineer be reflected on the file for the aircraft concerned. Accordingly there was no opportunity for the Archerfield-based officer carrying out the survey on the aircraft to check the configuration requirements prior to conducting a survey.

The first flight of VH-UNA after it was modified was conducted with the accident pilot in the frame. The pilot on that flight stated that he had difficulty climbing out of ground effect and that he was only able to attain a climb speed of 45 kts. The accident pilot is reported to have later stated that he had developed a slow flying technique that gave a climb performance acceptable to him. This technique is evident from videos taken at previous airshow performances which show the attitude difference between the accident aircraft and another Tiger Moth during takeoff.
(1994) - 2.3 Aircraft performance.
The propeller fitted to VH-UNA had a pitch of 4 ft 11 in, a standard cruise propeller for that aircraft.

The initial test on VH-GVA showed the aircraft to be performance-limited when fitted with a 4 ft 6 in pitch propeller. It was necessary to fit a fine-pitch propeller of 4 ft 2 in pitch to obtain a climb performance acceptable to that pilot. With a coarse pitch propeller fitted, VH-UNA would have been even more severely performance-limited than VH-GVA.

The pilot of VH-UNA possessed a copy of a Civil Aviation Authority letter that detailed the requirement to fit a fine-pitch propeller. It is not known why he did not comply with the requirement. However, had he fitted a fine-pitch propeller prior to departure from Brisbane, his cross-country cruise capability would have been degraded. The Authority's procedures for recording that the wing-walking frame had been installed onto VH-UNA were deficient.

Although the details were held on file in the Authority's Bankstown office in relation to the design engineer who approved the installation, they were not required to be copied to the aircraft file for VH-UNA which was held at Archerfield. The Queensland-based officer carrying out the survey on the aircraft would not have been aware from the data held on the aircraft file that the modification had been carried out some 12 months prior to the
survey. Nor would he have been aware of the conditions surrounding the installation and operation of the wing walking frame. Accordingly the chance to detect the incorrect propeller installation was missed.

[Old Akro]

Nice work Kharon

How is it that we do not get better at these things with the passage of time & technology. The 2013 ATSB author could have gathered the same information as the 194 one without leaving the air-conditioned comfort of his Canberra workstation

[Ex FSO GRIFFO]

Troo Mr Charlie,

Even in 'dem good ole days', JT would not let us in, sans tailwheel, as the skid would 'dig up their grass'.....
Plus taxying on the tarmac was an art form, skid, sans brakes etc.

Nowadays, 'tis radio, transponder & 'wheel' + brakes for de tarmac,which is really quite unforgiving of the little 'settling into the grass bounces' we all got used to.....
So 'wheelies' are the order of the day - mostly.

Good Times...
:ok::ok:

[dogcharlietree]

Tail skid was the best brake ever invented for grass. Short field landing. Hold stick right back, pulls up in it's own length AND keeps you straight. :ok:

[JammedStab]

Certainly more info could have been given. Field length, elevation etc.

It says that neither pilot reduced power after takeoff yet there was a decrease in performance and power was re-applied. The first thing that comes to my mind(keeping in mind that there are differences between Tiger Moths) is that the throttle friction was loose and the throttle moved aft due to it not being held forward.

But I don't know if there is a throttle friction knob on Tigers other than the one I fly.

[dubbleyew eight]

loss of engine performance in a tiger moth can occur.
I know of one that crashed from what appeared at the time to be carby icing.

what the problem actually was was something entirely different though.

up in the overhead tank there is a little one way overflow limiter with a bronze ball in it. it is supposed to seat on a little washer with one hole centrally and 3 holes at a radius around the centre hole.
over time and lots of maintenance the little washer gets lost. the result is that the bronze ball can wear itself a neat seat which seals beautifully.
in flight the bronze ball finally seals the air inlet and the fuel as it is used gradually sends the tank pressure below atmospheric and starves the engine of fuel.

when my friend jimmy experienced the crash and painstakingly worked out what the fault was he spoke to tiggy owners all over the world.
most tiggies, when checked, did not have the washer in place.
jimmy sent everyone a washer to put the matter to rest.

I may have the description slightly wrong but the broad gist of this is fact.