Aircraft HB-762, FFA Diamant: HBV, 16.5m and 18m versions

HB-762

Hi all

The Diamant came into being based on the specs of the Engineers Hütter, Bircher and van Voornfeld (HBV, 3 engineers of the department for aircraft design of the ETH, the federal technical highschool of Switzerland). Their design goal was the reduction of the drag of the fuselage using an almost lying position of the pilot (compared to the sitting attitude in a Ka-6). It was the first glider using a retractable wheel and a T-shaped tail to prevent damage to the elevator in out-landings in fields with high growth. They brought the idea to FFA (Flug- und Fahrzeugwerke Altenrhein in Switzerland) who produced 15 fuselages and elevators (sn 1 to 15) buying the wings from the Glasflügel Company in Germany. This series was called HBV Diamant in honour of the 3 engineers.

After the first 15 planes were built Mr Hähnle from Glasflügel did not want to sell more wings to FFA (he needed them for his own planes: Libelle H301). So FFA designed and built the wings on their own, but only in the 16.5m and 18m wingspan. These models were called Diamant 16.5m and Diamant 18m. Apparently the series numbers for the 16.5m and 18m versions started from 1, because there are several 16.5m planes listed with series nr smaller than 15.

So the correct names are

HBV Diamant (sn 1 to 15) for the 15 m version with Glasflügel wings

Diamant 16.5 for the 16.5m version with FFA wings

Diamant 18m for the 18m version with FFS wings

Diamant HBV HB-762 was never immatriculated in another country. So N292D must be either a 16.5 or 18m Diamant.

This information is certified based on a personal discussion with Mr. Bircher.

Kind regards

Peter Hanhart

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Hello Peter,

....I have however, carried out an Excel sort for all the FFA models we have in our database with the following results.

FFA Diamant HBV - 5 aircraft - cn's from 3 to 10

FFA Diamant HBV 16.5 - 17 aircraft - cn's from 12 to 50

FFA Diamant 16.5 - 12 aircraft - cn's from 11 to 63

FFA Diamant HBV 18 - 10 aircraft - cn's from 31 to 75

FFA Diamant 18 - 0 aircraft

Considering all models together, the cn's are sequential from 3 to 75 and none of the 16.5 models have a cn less than 11.

Also there are HBV listings for both the 16.5 and 18 rather than limiting HBV to the initial 15 aircraft...

Hi Malcolm

I do not know about the sequence of the c/n for the 16.5m and 18m Diamants. In Switzerland the HBV name was used only for the 15m versions. The reference to the 3 engineers Hütter, Bircher and van Voornfeld (=HBV) was dropped when fuselage AND wings were built by FFA. Maybe different names were used in the US for marketing reasons?

From my point of view we may close this item. The names HBV 16.5m and HBV 18m just popped onto my eyes when I stumbled over the airport data, in Switzerland they would be incorrect.

PS: I just checked old records. In 1974 a service Bulletin was released by FFA concerning the holdfast of the seatbelts:

Service Bulletin No 5 of Febr. 4 1974

Concerns all c/n:

DIAMANT HBV

DIAMANT 16.5

DIAMANT 18

Kind regards and a lot of respect for your work!

Peter

If it's the same ac in question, NTSB said it crashed in 1975/07/18

https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=48902&key=0

Walt

Hi Walt

I just checked the technical reocrds of my plane. Both wings of HB-762 were damaged about 1.5 m from the fuselage in pretty much the same way as N292D was. But this happened in Switzerland during a contest in May 1974 and the repair was finished by the Aeroclub repair crew. In 1975 only a normal service was made, no repairs.

In 1975 HB-762 was owned by a friend in the same glidergroup as I was flying. I know that the plane was never shipped to the US.

I am convinced that HB-762 and N292D are two different planes.

The c/n I found for HB-762 in the original bord book are:

Right wing: 10 R

Left wing: 10 L

Ringt aileron: 10 R

Left aileron: 10 L

Stabilizer: V3

Elevator: V3

Rudder: V3

Work Nr: V3

The wings have other numbers than the fuselage, since the wings were bought from the Glasflügel company.

Kind regards and a lot of respect for your work!

Peter

Walt, Peter,

I think that with your help we have reached as far as we may go on this matter.

The cn for N292D is in my view clearly in question.

My suggestions are

- to separate the two registrations into two unrelated profiles.

- add the NTSB reference as a remark to the N292D profile.

- remove the cn from N292D and add "see remarks".

- add a further remark to N292D referencing this Forum post and the uncertainty of

the FAA listed cn.

Malcolm.

Hi Malcolm and Walt

I agree with Malcolms suggestion. I will try and find somebody who may know more about the c/n, maybe even get a complete list. Since FFA stopped the support for this aircraft, it is officially "orphaned" and there may be no more original records available.

Thanks for all you are doing!

Peter